diff --git a/src/main/java/com/worksap/nlp/sudachi/JapaneseTokenizer.java b/src/main/java/com/worksap/nlp/sudachi/JapaneseTokenizer.java
index 09cc3f76..3af3b7a5 100644
--- a/src/main/java/com/worksap/nlp/sudachi/JapaneseTokenizer.java
+++ b/src/main/java/com/worksap/nlp/sudachi/JapaneseTokenizer.java
@@ -19,6 +19,7 @@
 import java.io.IOException;
 import java.io.PrintStream;
 import java.io.Reader;
+import java.io.StringReader;
 import java.io.StringWriter;
 import java.nio.CharBuffer;
 import java.util.ArrayList;
@@ -65,8 +66,9 @@ class JapaneseTokenizer implements Tokenizer {
     }
 
     @Override
-    public MorphemeList tokenize(Tokenizer.SplitMode mode, String text) {
+    public List<Morpheme> tokenize(Tokenizer.SplitMode mode, String text) {
         if (text.isEmpty()) {
+            // return MorphemeList instance for the case internalCost is required.
             return MorphemeList.EMPTY;
         }
         UTF8InputText input = buildInputText(text);
@@ -74,56 +76,45 @@ public MorphemeList tokenize(Tokenizer.SplitMode mode, String text) {
     }
 
     @Override
-    public Iterable<MorphemeList> tokenizeSentences(SplitMode mode, String text) {
+    public Iterable<List<Morpheme>> tokenizeSentences(SplitMode mode, String text) {
         if (text.isEmpty()) {
             return Collections.emptyList();
         }
 
-        SentenceSplittingAnalysis analysis = new SentenceSplittingAnalysis(mode, this);
-        int length = analysis.tokenizeBuffer(text);
-        ArrayList<MorphemeList> result = analysis.result;
-        int bos = analysis.bos;
-        if (length < 0) {
-            // treat remaining thing as a single sentence
-            int eos = analysis.input.getText().length();
-            if (bos != eos) {
-                UTF8InputText slice = analysis.input;
-                if (bos != 0) {
-                    slice = slice.slice(bos, eos);
-                }
-                result.add(tokenizeSentence(mode, slice));
-            }
-        }
+        StringReader input = new StringReader(text);
+        SentenceSplittingLazyAnalysis analysis = new SentenceSplittingLazyAnalysis(mode, this, input);
+        List<List<Morpheme>> result = new ArrayList<>();
+        analysis.forEachRemaining(result::add);
         return result;
     }
 
     @Override
-    public Iterable<MorphemeList> tokenizeSentences(SplitMode mode, Reader reader) throws IOException {
-        IOTools.SurrogateAwareReadable wrappedReader = new IOTools.SurrogateAwareReadable(reader);
-        CharBuffer buffer = CharBuffer.allocate(SentenceDetector.DEFAULT_LIMIT);
-        SentenceSplittingAnalysis analysis = new SentenceSplittingAnalysis(mode, this);
-
-        while (wrappedReader.read(buffer) > 0) {
-            buffer.flip();
-            int length = analysis.tokenizeBuffer(buffer);
-            if (length < 0) {
-                buffer.position(analysis.bosPosition());
-                buffer.compact();
-            }
-        }
-        buffer.flip();
-        ArrayList<MorphemeList> sentences = analysis.result;
-
-        if (buffer.hasRemaining()) {
-            sentences.add(tokenizeSentence(mode, buildInputText(buffer)));
-        }
+    public Iterator<List<Morpheme>> tokenizeSentences(SplitMode mode, Readable input) {
+        return new SentenceSplittingLazyAnalysis(mode, this, input);
+    }
 
-        return sentences;
+    @Override
+    public Iterator<List<Morpheme>> lazyTokenizeSentences(SplitMode mode, Readable input) {
+        return tokenizeSentences(mode, input);
     }
 
     @Override
-    public Iterator<List<Morpheme>> lazyTokenizeSentences(SplitMode mode, Readable readable) {
-        return new SentenceSplittingLazyAnalysis(mode, this, readable);
+    public List<Morpheme> split(List<Morpheme> morphemes, SplitMode mode) {
+        if (morphemes instanceof MorphemeList) {
+            return ((MorphemeList) morphemes).split(mode);
+        }
+
+        List<Morpheme> result = new ArrayList<>();
+        for (Morpheme m : morphemes) {
+            if (m instanceof SingleMorphemeImpl) {
+                ((SingleMorphemeImpl) m).appendSplitsTo(result, mode);
+            } else {
+                for (Morpheme subsplit : m.split(mode)) {
+                    result.add(subsplit);
+                }
+            }
+        }
+        return result;
     }
 
     @Override
@@ -161,7 +152,7 @@ UTF8InputText buildInputText(CharSequence text) {
         return input;
     }
 
-    MorphemeList tokenizeSentence(Tokenizer.SplitMode mode, UTF8InputText input) {
+    List<Morpheme> tokenizeSentence(Tokenizer.SplitMode mode, UTF8InputText input) {
         checkIfAlive();
         buildLattice(input);
 
diff --git a/src/main/java/com/worksap/nlp/sudachi/LatticeNodeImpl.java b/src/main/java/com/worksap/nlp/sudachi/LatticeNodeImpl.java
index 385f214e..907bcfb5 100644
--- a/src/main/java/com/worksap/nlp/sudachi/LatticeNodeImpl.java
+++ b/src/main/java/com/worksap/nlp/sudachi/LatticeNodeImpl.java
@@ -215,15 +215,7 @@ public StringsCache getStrings() {
     }
 
     /* internal */ void appendSplitsTo(List<LatticeNodeImpl> result, Tokenizer.SplitMode mode) {
-        if (mode == Tokenizer.SplitMode.A) {
-            appendSplitsTo(result, getWordInfo().getAunitSplit());
-        } else if (mode == Tokenizer.SplitMode.B) {
-            appendSplitsTo(result, getWordInfo().getBunitSplit());
-        } else if (mode == Tokenizer.SplitMode.C) {
-            appendSplitsTo(result, getWordInfo().getCunitSplit());
-        } else {
-            result.add(this);
-        }
+        appendSplitsTo(result, getWordInfo().getUnitSplit(mode));
     }
 
     private void appendSplitsTo(List<LatticeNodeImpl> result, int[] splitsId) {
diff --git a/src/main/java/com/worksap/nlp/sudachi/MorphemeList.java b/src/main/java/com/worksap/nlp/sudachi/MorphemeList.java
index 21571e9b..df3fdc4d 100644
--- a/src/main/java/com/worksap/nlp/sudachi/MorphemeList.java
+++ b/src/main/java/com/worksap/nlp/sudachi/MorphemeList.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021 Works Applications Co., Ltd.
+ * Copyright (c) 2021-2024 Works Applications Co., Ltd.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -48,7 +48,7 @@ public class MorphemeList extends AbstractList<Morpheme> {
     }
 
     @Override
-    public Morpheme get(int index) {
+    public MorphemeListItem get(int index) {
         return new MorphemeListItem(this, index);
     }
 
@@ -91,7 +91,7 @@ WordInfo getWordInfo(int index) {
         return path.get(index).getWordInfo();
     }
 
-    List<Morpheme> split(Tokenizer.SplitMode mode, int index) {
+    MorphemeList split(Tokenizer.SplitMode mode, int index) {
         List<LatticeNodeImpl> nodes = new ArrayList<>();
         LatticeNodeImpl node = path.get(index);
         node.appendSplitsTo(nodes, mode);
@@ -106,18 +106,19 @@ List<Morpheme> split(Tokenizer.SplitMode mode, int index) {
      * @param mode
      *            requested split mode
      * @return current list or a new list in the requested split mode.
+     * 
+     * @deprecated will be internal only. use {@link Tokenizer#split} instead.
      */
+    @Deprecated
     public MorphemeList split(Tokenizer.SplitMode mode) {
         if (mode.compareTo(this.mode) >= 0) {
             return this;
         }
 
         List<LatticeNodeImpl> nodes = new ArrayList<>();
-
         for (LatticeNodeImpl node : path) {
             node.appendSplitsTo(nodes, mode);
         }
-
         return new MorphemeList(inputText, grammar, lexicon, nodes, allowEmptyMorpheme, mode);
     }
 
diff --git a/src/main/java/com/worksap/nlp/sudachi/MorphemeListItem.java b/src/main/java/com/worksap/nlp/sudachi/MorphemeListItem.java
index e58d8fc6..125fd853 100644
--- a/src/main/java/com/worksap/nlp/sudachi/MorphemeListItem.java
+++ b/src/main/java/com/worksap/nlp/sudachi/MorphemeListItem.java
@@ -77,7 +77,7 @@ public String surface() {
     }
 
     @Override
-    public List<Morpheme> split(Tokenizer.SplitMode mode) {
+    public MorphemeList split(Tokenizer.SplitMode mode) {
         return list.split(mode, index);
     }
 
diff --git a/src/main/java/com/worksap/nlp/sudachi/SentenceSplittingAnalysis.java b/src/main/java/com/worksap/nlp/sudachi/SentenceSplittingAnalysis.java
deleted file mode 100644
index 254e0e51..00000000
--- a/src/main/java/com/worksap/nlp/sudachi/SentenceSplittingAnalysis.java
+++ /dev/null
@@ -1,93 +0,0 @@
-/*
- * Copyright (c) 2023 Works Applications Co., Ltd.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.worksap.nlp.sudachi;
-
-import com.worksap.nlp.sudachi.dictionary.LexiconSet;
-import com.worksap.nlp.sudachi.sentdetect.SentenceDetector;
-
-import java.util.ArrayList;
-import java.util.Iterator;
-
-/*internal*/ class SentenceSplittingAnalysis implements SentenceDetector.NonBreakCheker {
-    private final SentenceDetector detector = new SentenceDetector();
-
-    private final Tokenizer.SplitMode mode;
-    private final JapaneseTokenizer tokenizer;
-    final ArrayList<MorphemeList> result = new ArrayList<>();
-
-    SentenceSplittingAnalysis(Tokenizer.SplitMode mode, JapaneseTokenizer tokenizer) {
-        this.mode = mode;
-        this.tokenizer = tokenizer;
-    }
-
-    UTF8InputText input;
-    int bos;
-
-    int tokenizeBuffer(CharSequence buffer) {
-        UTF8InputText input = tokenizer.buildInputText(buffer);
-        String normalized = input.getText();
-        this.input = input;
-
-        int bos = 0;
-        int length;
-
-        this.bos = bos;
-        while ((length = detector.getEos(normalized, this)) > 0) {
-            int eos = bos + length;
-            if (eos < normalized.length()) {
-                eos = input.getNextInOriginal(eos - 1);
-                length = eos - bos;
-            }
-            UTF8InputText sentence = input.slice(bos, eos);
-            result.add(tokenizer.tokenizeSentence(mode, sentence));
-            normalized = normalized.substring(length);
-            bos = eos;
-            this.bos = bos;
-        }
-
-        // buffer is full, need to clean it up
-        if (length < 0 && buffer.length() == -length) {
-            result.add(tokenizer.tokenizeSentence(mode, input));
-            return -length;
-        }
-
-        return length;
-    }
-
-    int bosPosition() {
-        return input.textIndexToOriginalTextIndex(bos);
-    }
-
-    @Override
-    public boolean hasNonBreakWord(int length) {
-        UTF8InputText inp = input;
-        int byteEOS = inp.getCodePointsOffsetLength(0, bos + length);
-        byte[] bytes = inp.getByteText();
-        LexiconSet lexicon = tokenizer.lexicon;
-        for (int i = Math.max(0, byteEOS - 64); i < byteEOS; i++) {
-            Iterator<int[]> iterator = lexicon.lookup(bytes, i);
-            while (iterator.hasNext()) {
-                int[] r = iterator.next();
-                int l = r[1];
-                if (l > byteEOS || (l == byteEOS && bos + length - inp.modifiedOffset(i) > 1)) {
-                    return true;
-                }
-            }
-        }
-        return false;
-    }
-}
diff --git a/src/main/java/com/worksap/nlp/sudachi/SentenceSplittingLazyAnalysis.java b/src/main/java/com/worksap/nlp/sudachi/SentenceSplittingLazyAnalysis.java
index 44ebfdce..72eb9caf 100644
--- a/src/main/java/com/worksap/nlp/sudachi/SentenceSplittingLazyAnalysis.java
+++ b/src/main/java/com/worksap/nlp/sudachi/SentenceSplittingLazyAnalysis.java
@@ -100,7 +100,7 @@ public boolean hasNext() {
     }
 
     @Override
-    public MorphemeList next() {
+    public List<Morpheme> next() {
         int length = detector.getEos(normalized, this);
         if (length > 0) { // sentence found
             int eos = bos + length;
diff --git a/src/main/java/com/worksap/nlp/sudachi/SingleMorphemeImpl.java b/src/main/java/com/worksap/nlp/sudachi/SingleMorphemeImpl.java
index 55cdc87e..a8f2d482 100644
--- a/src/main/java/com/worksap/nlp/sudachi/SingleMorphemeImpl.java
+++ b/src/main/java/com/worksap/nlp/sudachi/SingleMorphemeImpl.java
@@ -118,16 +118,8 @@ public List<Morpheme> split(Tokenizer.SplitMode mode) {
      * 
      * @see LatticeNodeImpl.appendSplitsTo
      */
-    private void appendSplitsTo(List<Morpheme> result, Tokenizer.SplitMode mode) {
-        if (mode == Tokenizer.SplitMode.A) {
-            appendSplitsTo(result, getWordInfo().getAunitSplit());
-        } else if (mode == Tokenizer.SplitMode.B) {
-            appendSplitsTo(result, getWordInfo().getBunitSplit());
-        } else if (mode == Tokenizer.SplitMode.C) {
-            appendSplitsTo(result, getWordInfo().getCunitSplit());
-        } else {
-            result.add(this);
-        }
+    /* internal */ void appendSplitsTo(List<Morpheme> result, Tokenizer.SplitMode mode) {
+        appendSplitsTo(result, getWordInfo().getUnitSplit(mode));
     }
 
     private void appendSplitsTo(List<Morpheme> result, int[] splitIds) {
diff --git a/src/main/java/com/worksap/nlp/sudachi/Tokenizer.java b/src/main/java/com/worksap/nlp/sudachi/Tokenizer.java
index 89f6adef..95e2f1aa 100644
--- a/src/main/java/com/worksap/nlp/sudachi/Tokenizer.java
+++ b/src/main/java/com/worksap/nlp/sudachi/Tokenizer.java
@@ -37,7 +37,7 @@ public interface Tokenizer {
      *            input text
      * @return a result of tokenizing
      */
-    MorphemeList tokenize(SplitMode mode, String text);
+    List<Morpheme> tokenize(SplitMode mode, String text);
 
     /**
      *
@@ -48,7 +48,7 @@ public interface Tokenizer {
      * @return a result of tokenizing
      * @see #tokenize(SplitMode,String)
      */
-    default MorphemeList tokenize(final String text) {
+    default List<Morpheme> tokenize(final String text) {
         return tokenize(SplitMode.C, text);
     }
 
@@ -62,7 +62,7 @@ default MorphemeList tokenize(final String text) {
      *            input text
      * @return a result of tokenizing
      */
-    Iterable<MorphemeList> tokenizeSentences(SplitMode mode, String text);
+    Iterable<List<Morpheme>> tokenizeSentences(SplitMode mode, String text);
 
     /**
      * Tokenize sentences. Divide an input text into sentences and tokenize them
@@ -73,42 +73,32 @@ default MorphemeList tokenize(final String text) {
      * @return a result of tokenizing
      * @see #tokenizeSentences(SplitMode,String)
      */
-    default Iterable<MorphemeList> tokenizeSentences(String text) {
+    default Iterable<List<Morpheme>> tokenizeSentences(String text) {
         return tokenizeSentences(SplitMode.C, text);
     }
 
     /**
      * Read an input text from {@code input}, divide it into sentences and tokenize
-     * them. It reads all text in the input and uses a lot of memory when the text
-     * is long.
+     * them. It reads the input lazily.
      *
      * @param mode
      *            a mode of splitting
      * @param input
-     *            a reader of input text
-     * @return a result of tokenizing
-     * @throws IOException
-     *             if reading a stream is failed
-     * @deprecated use {@link #lazyTokenizeSentences(SplitMode, Readable)} instead.
+     *            a readable input text
+     * @return an iterator of tokenized sentences
      */
-    @Deprecated
-    Iterable<MorphemeList> tokenizeSentences(SplitMode mode, Reader input) throws IOException;
+    Iterator<List<Morpheme>> tokenizeSentences(SplitMode mode, Readable input);
 
     /**
-     * Reads an input text from {@code input}, divide it into sentences and
-     * tokenizes them with {@link SplitMode}.C. It reads all text in the input and
-     * uses a lot of memory when the text is long.
+     * Read an input text from {@code input}, divide it into sentences and tokenize
+     * them with {@link SplitMode}.C. It reads the input lazily.
      *
      * @param input
-     *            a reader of input text
-     * @return a result of tokenizing
-     * @throws IOException
-     *             if reading a stream is failed
-     * @see #tokenizeSentences(SplitMode,Reader)
-     * @deprecated use {@link #lazyTokenizeSentences(Readable)} instead.
+     *            a readable input text
+     * @return an iterator of tokenized sentences
+     * @see #tokenizeSentences(SplitMode,Readable)
      */
-    @Deprecated
-    default Iterable<MorphemeList> tokenizeSentences(Reader input) throws IOException {
+    default Iterator<List<Morpheme>> tokenizeSentences(Readable input) {
         return tokenizeSentences(SplitMode.C, input);
     }
 
@@ -121,7 +111,10 @@ default Iterable<MorphemeList> tokenizeSentences(Reader input) throws IOExceptio
      * @param input
      *            a readable input text
      * @return a result of tokenizing
+     * @deprecated renamed to {@link #tokenizeSentences(SplitMode, Readable)}
+     * 
      */
+    @Deprecated
     Iterator<List<Morpheme>> lazyTokenizeSentences(SplitMode mode, Readable input);
 
     /**
@@ -132,11 +125,25 @@ default Iterable<MorphemeList> tokenizeSentences(Reader input) throws IOExceptio
      *            a readable input text
      * @return a result of tokenizing
      * @see #lazyTokenizeSentences(SplitMode,Readable)
+     * @deprecated renamed to {@link #tokenizeSentences(Readable)}
      */
+    @Deprecated
     default Iterator<List<Morpheme>> lazyTokenizeSentences(Readable input) {
         return lazyTokenizeSentences(SplitMode.C, input);
     }
 
+    /**
+     * Produce a copy of this list in a finer split mode. May return the given list
+     * if the mode is coarser than the current one. The given list is not modified.
+     * 
+     * @param morphemes
+     *            list of morphemes to split.
+     * @param mode
+     *            requested split mode
+     * @return current list, or a new list in the requested split mode.
+     */
+    List<Morpheme> split(List<Morpheme> morphemes, SplitMode mode);
+
     /**
      * Prints lattice structure of the analysis into the passed {@link PrintStream}.
      *
diff --git a/src/main/java/com/worksap/nlp/sudachi/dictionary/DoubleArrayLexicon.java b/src/main/java/com/worksap/nlp/sudachi/dictionary/DoubleArrayLexicon.java
index 844a6b98..9f3677a8 100644
--- a/src/main/java/com/worksap/nlp/sudachi/dictionary/DoubleArrayLexicon.java
+++ b/src/main/java/com/worksap/nlp/sudachi/dictionary/DoubleArrayLexicon.java
@@ -208,7 +208,7 @@ public void calculateDynamicCosts(Tokenizer tokenizer) {
                 }
                 int headwordPtr = wordInfos.headwordPtr(wordId);
                 String headword = strings.string(headwordPtr);
-                MorphemeList ms = tokenizer.tokenize(headword);
+                MorphemeList ms = (MorphemeList) tokenizer.tokenize(headword);
                 int cost = ms.getInternalCost() + USER_DICT_COST_PAR_MORPH * ms.size();
                 if (cost > Short.MAX_VALUE) {
                     cost = Short.MAX_VALUE;
diff --git a/src/main/java/com/worksap/nlp/sudachi/dictionary/WordInfo.java b/src/main/java/com/worksap/nlp/sudachi/dictionary/WordInfo.java
index 8da239d6..9ccd2acb 100644
--- a/src/main/java/com/worksap/nlp/sudachi/dictionary/WordInfo.java
+++ b/src/main/java/com/worksap/nlp/sudachi/dictionary/WordInfo.java
@@ -16,10 +16,11 @@
 
 package com.worksap.nlp.sudachi.dictionary;
 
-import com.worksap.nlp.sudachi.StringUtil;
-
 import java.nio.ByteBuffer;
 
+import com.worksap.nlp.sudachi.StringUtil;
+import com.worksap.nlp.sudachi.Tokenizer;
+
 /**
  * Internal morpheme information. This class does not contain any strings.
  *
@@ -186,6 +187,23 @@ public int[] getCunitSplit() {
         return cUnitSplit;
     }
 
+    /**
+     * Returns the array of word IDs which the morpheme is compounded of in given
+     * mode.
+     * 
+     * @return the word IDs of the given units
+     */
+    public int[] getUnitSplit(Tokenizer.SplitMode mode) {
+        if (mode == Tokenizer.SplitMode.A) {
+            return getAunitSplit();
+        }
+        if (mode == Tokenizer.SplitMode.B) {
+            return getBunitSplit();
+        }
+        assert (mode == Tokenizer.SplitMode.C);
+        return getCunitSplit();
+    }
+
     /**
      * Returns the array of the morphemes which the morpheme is compounded of.
      *
diff --git a/src/test/java/com/worksap/nlp/sudachi/JapaneseTokenizerStreamingTest.kt b/src/test/java/com/worksap/nlp/sudachi/JapaneseTokenizerStreamingTest.kt
index 85aebbae..c77467bd 100644
--- a/src/test/java/com/worksap/nlp/sudachi/JapaneseTokenizerStreamingTest.kt
+++ b/src/test/java/com/worksap/nlp/sudachi/JapaneseTokenizerStreamingTest.kt
@@ -26,6 +26,35 @@ import kotlin.test.assertFailsWith
 class JapaneseTokenizerStreamingTest {
   private val tokenizer = TestDictionary.user0().tokenizer()
 
+  @Test
+  fun streamingReadable() {
+    val reader = StringReader("あ".repeat(5000))
+    val result = tokenizer.tokenizeSentences(Tokenizer.SplitMode.C, reader).asSequence()
+    val totalLength = result.sumOf { sent -> sent.sumOf { mrph -> mrph.end() - mrph.begin() } }
+    assertEquals(5000, totalLength)
+  }
+
+  @Test
+  fun callingNextWithoutTextFails() {
+    val reader = StringReader("東京")
+    val it = tokenizer.tokenizeSentences(Tokenizer.SplitMode.C, reader)
+
+    val morphemes = it.next()
+    assertEquals("東京", morphemes.get(0).surface())
+
+    assertFailsWith<java.util.NoSuchElementException>(
+        block = { it.next() },
+    )
+  }
+
+  @Test
+  fun streamingLongTextShouldNotCauseOOM() {
+    val reader = StringReader("あ".repeat(10 * 1024 * 1024))
+    val result = tokenizer.tokenizeSentences(Tokenizer.SplitMode.C, reader).asSequence()
+    val totalLength = result.sumOf { sent -> sent.sumOf { mrph -> mrph.end() - mrph.begin() } }
+    assertEquals(10 * 1024 * 1024, totalLength)
+  }
+
   class BadReader(private val data: String, private val window: Int = 512) : Reader() {
 
     private var position: Int = 0
@@ -50,61 +79,14 @@ class JapaneseTokenizerStreamingTest {
     override fun close() {}
   }
 
-  @Test
-  fun streamingTest() {
-    // Testing deprecated method `tokenizeSentences(Reader)`
-    val reader = StringReader("あ".repeat(5000))
-    val result = tokenizer.tokenizeSentences(Tokenizer.SplitMode.C, reader)
-    val totalLength = result.sumOf { sent -> sent.sumOf { mrph -> mrph.end() - mrph.begin() } }
-    assertEquals(5000, totalLength)
-  }
-
-  @Test
-  fun streamingTestWithBadReader() {
-    // Testing deprecated method `tokenizeSentences(Reader)`
-    val reader = BadReader("あ".repeat(5000))
-    val result = tokenizer.tokenizeSentences(Tokenizer.SplitMode.C, reader)
-    val totalLength = result.sumOf { sent -> sent.sumOf { mrph -> mrph.end() - mrph.begin() } }
-    assertEquals(5000, totalLength)
-  }
-
-  @Test
-  fun streamingReadable() {
-    val reader = StringReader("あ".repeat(5000))
-    val result = tokenizer.lazyTokenizeSentences(Tokenizer.SplitMode.C, reader).asSequence()
-    val totalLength = result.sumOf { sent -> sent.sumOf { mrph -> mrph.end() - mrph.begin() } }
-    assertEquals(5000, totalLength)
-  }
-
-  @Test
-  fun callingNextWithoutTextFails() {
-    val reader = StringReader("東京")
-    val it = tokenizer.lazyTokenizeSentences(Tokenizer.SplitMode.C, reader)
-
-    val morphemes = it.next()
-    assertEquals("東京", morphemes.get(0).surface())
-
-    assertFailsWith<java.util.NoSuchElementException>(
-        block = { it.next() },
-    )
-  }
-
   @Test
   fun streamingBlockingReadable() {
     val reader = BadReader("あ".repeat(5000))
-    val result = tokenizer.lazyTokenizeSentences(Tokenizer.SplitMode.C, reader).asSequence()
+    val result = tokenizer.tokenizeSentences(Tokenizer.SplitMode.C, reader).asSequence()
     val totalLength = result.sumOf { sent -> sent.sumOf { mrph -> mrph.end() - mrph.begin() } }
     assertEquals(5000, totalLength)
   }
 
-  @Test
-  fun streamingLongTextShouldNotCauseOOM() {
-    val reader = StringReader("あ".repeat(10 * 1024 * 1024))
-    val result = tokenizer.lazyTokenizeSentences(Tokenizer.SplitMode.C, reader).asSequence()
-    val totalLength = result.sumOf { sent -> sent.sumOf { mrph -> mrph.end() - mrph.begin() } }
-    assertEquals(10 * 1024 * 1024, totalLength)
-  }
-
   class FailReader(private val data: String) : Reader() {
 
     private var position: Int = 0
@@ -133,13 +115,13 @@ class JapaneseTokenizerStreamingTest {
   fun failsWhenReaderFails() {
     var reader = FailReader("あ".repeat(500))
     // should not fail on the instantiation
-    var it = tokenizer.lazyTokenizeSentences(Tokenizer.SplitMode.C, reader)
+    var it = tokenizer.tokenizeSentences(Tokenizer.SplitMode.C, reader)
     assertFailsWith<java.io.UncheckedIOException>(
         block = { it.hasNext() },
     )
 
     reader = FailReader("あ".repeat(500))
-    it = tokenizer.lazyTokenizeSentences(Tokenizer.SplitMode.C, reader)
+    it = tokenizer.tokenizeSentences(Tokenizer.SplitMode.C, reader)
     assertFailsWith<java.io.UncheckedIOException>(
         block = { it.next() },
     )
diff --git a/src/test/java/com/worksap/nlp/sudachi/JapaneseTokenizerTest.java b/src/test/java/com/worksap/nlp/sudachi/JapaneseTokenizerTest.java
index 50494e85..f34a3abf 100644
--- a/src/test/java/com/worksap/nlp/sudachi/JapaneseTokenizerTest.java
+++ b/src/test/java/com/worksap/nlp/sudachi/JapaneseTokenizerTest.java
@@ -27,6 +27,7 @@
 import java.io.StringReader;
 import java.util.Iterator;
 import java.util.List;
+import java.util.ArrayList;
 
 import javax.json.Json;
 import javax.json.JsonArray;
@@ -140,7 +141,7 @@ public void tokenizeKanjiAlphabetWord() {
 
     @Test
     public void tokenizeSentences() {
-        Iterator<MorphemeList> it = tokenizer.tokenizeSentences("京都。東京.東京都。").iterator();
+        Iterator<List<Morpheme>> it = tokenizer.tokenizeSentences("京都。東京.東京都。").iterator();
         assertThat(it.hasNext(), is(true));
         assertThat(it.next().size(), is(2));
         assertThat(it.hasNext(), is(true));
@@ -157,7 +158,7 @@ public void tokenizeSentences() {
 
     @Test
     public void tokenizerWithDots() {
-        MorphemeList s = tokenizer.tokenize("京都…");
+        List<Morpheme> s = tokenizer.tokenize("京都…");
         assertThat(s.size(), is(4));
         assertThat(s.get(1).surface(), is("…"));
         assertThat(s.get(1).normalizedForm(), is("."));
@@ -169,7 +170,7 @@ public void tokenizerWithDots() {
 
     @Test
     public void tokenizerWithModifiedChar() {
-        Iterator<MorphemeList> it = tokenizer.tokenizeSentences("´´").iterator();
+        Iterator<List<Morpheme>> it = tokenizer.tokenizeSentences("´´").iterator();
         assertThat(it.hasNext(), is(true));
         assertThat(it.next().size(), is(4));
         assertThat(it.hasNext(), is(false));
@@ -177,7 +178,7 @@ public void tokenizerWithModifiedChar() {
 
     @Test
     public void tokenizeSentencesWithSurrogatePair() {
-        Iterator<MorphemeList> it = tokenizer.tokenizeSentences("。😀").iterator();
+        Iterator<List<Morpheme>> it = tokenizer.tokenizeSentences("。😀").iterator();
         assertThat(it.hasNext(), is(true));
         assertThat(it.next().size(), is(1));
         assertThat(it.hasNext(), is(true));
@@ -185,15 +186,10 @@ public void tokenizeSentencesWithSurrogatePair() {
         assertThat(it.hasNext(), is(false));
     }
 
-    /**
-     * @deprecated testing deprecated method
-     *             {@link #Tokenizer.tokenizeSentences(Reader)}.
-     */
-    @Deprecated
     @Test
     public void tokenizerWithReader() throws IOException {
         StringReader reader = new StringReader("京都。東京.東京都。京都");
-        Iterator<MorphemeList> it = tokenizer.tokenizeSentences(reader).iterator();
+        Iterator<List<Morpheme>> it = tokenizer.tokenizeSentences(reader);
         assertThat(it.hasNext(), is(true));
         assertThat(it.next().size(), is(2));
         assertThat(it.hasNext(), is(true));
@@ -205,11 +201,6 @@ public void tokenizerWithReader() throws IOException {
         assertThat(it.hasNext(), is(false));
     }
 
-    /**
-     * @deprecated testing deprecated method
-     *             {@link #Tokenizer.tokenizeSentences(Reader)}.
-     */
-    @Deprecated
     @Test
     public void tokenizerWithLongReader() throws IOException {
         StringBuilder sb = new StringBuilder();
@@ -218,7 +209,7 @@ public void tokenizerWithLongReader() throws IOException {
         }
         sb.append("京都");
         StringReader reader = new StringReader(sb.toString());
-        Iterator<MorphemeList> it = tokenizer.tokenizeSentences(reader).iterator();
+        Iterator<List<Morpheme>> it = tokenizer.tokenizeSentences(reader);
         for (int i = 0; i < SentenceDetector.DEFAULT_LIMIT * 2 / 3; i++) {
             assertThat(it.hasNext(), is(true));
             assertThat(it.next().size(), is(2));
@@ -228,11 +219,6 @@ public void tokenizerWithLongReader() throws IOException {
         assertThat(it.hasNext(), is(false));
     }
 
-    /**
-     * @deprecated testing deprecated method
-     *             {@link #Tokenizer.tokenizeSentences(Reader)}.
-     */
-    @Deprecated
     @Test
     public void tokenizerWithReaderAndNormalization() throws IOException {
         StringBuilder sb = new StringBuilder();
@@ -241,7 +227,7 @@ public void tokenizerWithReaderAndNormalization() throws IOException {
             sb.append("京都。");
         }
         StringReader reader = new StringReader(sb.toString());
-        Iterator<MorphemeList> it = tokenizer.tokenizeSentences(reader).iterator();
+        Iterator<List<Morpheme>> it = tokenizer.tokenizeSentences(reader);
         assertThat(it.hasNext(), is(true));
         assertThat(it.next().size(), is(5));
         for (int i = 0; i < SentenceDetector.DEFAULT_LIMIT / 3; i++) {
@@ -254,6 +240,28 @@ public void tokenizerWithReaderAndNormalization() throws IOException {
         assertThat(it.hasNext(), is(false));
     }
 
+    @Test
+    public void tokenizeSentencesWithSurrogatePairAtBufferLimit() {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < SentenceDetector.DEFAULT_LIMIT - 1; i++) {
+            sb.append("。");
+        }
+        sb.append("😀");
+        StringReader reader = new StringReader(sb.toString());
+        Iterator<List<Morpheme>> it = tokenizer.tokenizeSentences(reader);
+
+        assertThat(it.hasNext(), is(true));
+        assertThat(it.next().size(), is(SentenceDetector.DEFAULT_LIMIT - 1));
+        assertThat(it.hasNext(), is(true));
+        assertThat(it.next().size(), is(1));
+        assertThat(it.hasNext(), is(false));
+    }
+
+    /**
+     * @deprecated testing deprecated method
+     *             {@link #Tokenizer.lazyTokenizeSentences(Readable)}.
+     */
+    @Deprecated
     @Test
     public void lazyTokenizeSentences() {
         StringReader reader = new StringReader("京都。東京.東京都。京都");
@@ -275,6 +283,11 @@ public void lazyTokenizeSentences() {
         assertThat(it.hasNext(), is(false));
     }
 
+    /**
+     * @deprecated testing deprecated method
+     *             {@link #Tokenizer.lazyTokenizeSentences(Readable)}.
+     */
+    @Deprecated
     @Test
     public void lazyTokenizeSentencesWithLongText() {
         StringBuilder sb = new StringBuilder();
@@ -293,6 +306,11 @@ public void lazyTokenizeSentencesWithLongText() {
         assertThat(it.hasNext(), is(false));
     }
 
+    /**
+     * @deprecated testing deprecated method
+     *             {@link #Tokenizer.lazyTokenizeSentences(Readable)}.
+     */
+    @Deprecated
     @Test
     public void lazyTokenizeSentencesWithNormalization() {
         StringBuilder sb = new StringBuilder();
@@ -314,23 +332,6 @@ public void lazyTokenizeSentencesWithNormalization() {
         assertThat(it.hasNext(), is(false));
     }
 
-    @Test
-    public void lazyTokenizeSentencesWithSurrogatePair() {
-        StringBuilder sb = new StringBuilder();
-        for (int i = 0; i < SentenceDetector.DEFAULT_LIMIT - 1; i++) {
-            sb.append("。");
-        }
-        sb.append("😀");
-        StringReader reader = new StringReader(sb.toString());
-        Iterator<List<Morpheme>> it = tokenizer.lazyTokenizeSentences(reader);
-
-        assertThat(it.hasNext(), is(true));
-        assertThat(it.next().size(), is(SentenceDetector.DEFAULT_LIMIT - 1));
-        assertThat(it.hasNext(), is(true));
-        assertThat(it.next().size(), is(1));
-        assertThat(it.hasNext(), is(false));
-    }
-
     @Test
     public void zeroLengthMorpheme() {
         List<Morpheme> s = tokenizer.tokenize("…");
@@ -373,7 +374,7 @@ public void disableEmptyMorpheme() throws IOException {
 
     @Test
     public void splitC() {
-        MorphemeList morphemesC = tokenizer.tokenize(Tokenizer.SplitMode.C, "東東京都");
+        List<Morpheme> morphemesC = tokenizer.tokenize(Tokenizer.SplitMode.C, "東東京都");
         assertThat(morphemesC.get(0).surface(), is("東"));
         assertThat(morphemesC.get(1).surface(), is("東"));
         assertThat(morphemesC.get(2).surface(), is("京都"));
@@ -381,54 +382,54 @@ public void splitC() {
 
     @Test
     public void splitAfterTokenizeCtoA() {
-        MorphemeList morphemesC = tokenizer.tokenize(Tokenizer.SplitMode.C, "東京都");
+        List<Morpheme> morphemesC = tokenizer.tokenize(Tokenizer.SplitMode.C, "東京都");
         assertThat(morphemesC.size(), is(1));
-        MorphemeList morphemesA = morphemesC.split(Tokenizer.SplitMode.A);
+        List<Morpheme> morphemesA = tokenizer.split(morphemesC, Tokenizer.SplitMode.A);
         assertThat(morphemesA.size(), is(2));
     }
 
     @Test
     public void splitAfterTokenizeCtoB() {
-        MorphemeList morphemesC = tokenizer.tokenize(Tokenizer.SplitMode.C, "東京都");
+        List<Morpheme> morphemesC = tokenizer.tokenize(Tokenizer.SplitMode.C, "東京都");
         assertThat(morphemesC.size(), is(1));
-        MorphemeList morphemesB = morphemesC.split(Tokenizer.SplitMode.B);
+        List<Morpheme> morphemesB = tokenizer.split(morphemesC, Tokenizer.SplitMode.B);
         assertThat(morphemesB.size(), is(1));
     }
 
     @Test
     public void splitAfterTokenizeCtoC() {
-        MorphemeList morphemes1 = tokenizer.tokenize(Tokenizer.SplitMode.C, "東京都");
+        List<Morpheme> morphemes1 = tokenizer.tokenize(Tokenizer.SplitMode.C, "東京都");
         assertThat(morphemes1.size(), is(1));
-        MorphemeList morphemes2 = morphemes1.split(Tokenizer.SplitMode.C);
+        List<Morpheme> morphemes2 = tokenizer.split(morphemes1, Tokenizer.SplitMode.C);
         assertThat(morphemes2, sameInstance(morphemes1));
     }
 
     @Test
     public void splitAfterTokenizeAtoC() {
-        MorphemeList morphemes1 = tokenizer.tokenize(Tokenizer.SplitMode.A, "東京都");
+        List<Morpheme> morphemes1 = tokenizer.tokenize(Tokenizer.SplitMode.A, "東京都");
         assertThat(morphemes1.size(), is(2));
-        MorphemeList morphemes2 = morphemes1.split(Tokenizer.SplitMode.C);
+        List<Morpheme> morphemes2 = tokenizer.split(morphemes1, Tokenizer.SplitMode.C);
         assertThat(morphemes2, sameInstance(morphemes1));
     }
 
     @Test
     public void splitAfterTokenizeBtoC() {
-        MorphemeList morphemes1 = tokenizer.tokenize(Tokenizer.SplitMode.B, "東京都");
+        List<Morpheme> morphemes1 = tokenizer.tokenize(Tokenizer.SplitMode.B, "東京都");
         assertThat(morphemes1.size(), is(1));
-        MorphemeList morphemes2 = morphemes1.split(Tokenizer.SplitMode.C);
+        List<Morpheme> morphemes2 = tokenizer.split(morphemes1, Tokenizer.SplitMode.C);
         assertThat(morphemes2, sameInstance(morphemes1));
     }
 
     @Test
     public void splitWithZeroWidthTokens() {
-        MorphemeList morphemes1 = tokenizer.tokenize("…東京都…");
+        List<Morpheme> morphemes1 = tokenizer.tokenize("…東京都…");
         assertThat(morphemes1.size(), is(7));
         assertThat(morphemes1.get(0), morpheme("…", 0, 1));
         assertThat(morphemes1.get(1), morpheme("", 1, 1));
         assertThat(morphemes1.get(2), morpheme("", 1, 1));
         assertThat(morphemes1.get(3), morpheme("東京都", 1, 4));
         assertThat(morphemes1.get(4), morpheme("…", 4, 5));
-        MorphemeList morphemes2 = morphemes1.split(Tokenizer.SplitMode.A);
+        List<Morpheme> morphemes2 = tokenizer.split(morphemes1, Tokenizer.SplitMode.A);
         assertThat(morphemes2.size(), is(8));
         assertThat(morphemes2.get(3), morpheme("東京", 1, 3));
         assertThat(morphemes2.get(4), morpheme("都", 3, 4));
@@ -436,14 +437,42 @@ public void splitWithZeroWidthTokens() {
 
     @Test
     public void splitSingleToken() {
-        MorphemeList morphemes1 = tokenizer.tokenize(Tokenizer.SplitMode.C, "な。な");
+        List<Morpheme> morphemes1 = tokenizer.tokenize(Tokenizer.SplitMode.C, "な。な");
         assertThat(morphemes1.size(), is(1));
         assertThat(morphemes1.get(0), morpheme("な。な", 0, 3));
-        MorphemeList morphemes2 = morphemes1.split(Tokenizer.SplitMode.A);
+        List<Morpheme> morphemes2 = tokenizer.split(morphemes1, Tokenizer.SplitMode.A);
         assertThat(morphemes2.get(0), morpheme("な。な", 0, 3));
         assertThat(morphemes2.get(0).normalizedForm(), is("アイウ"));
     }
 
+    @Test
+    public void splitListOfSingleMorphemes() {
+        List<Morpheme> morphemes = new ArrayList<>();
+
+        morphemes.add(dict.lookup("京都").get(0));
+        morphemes.add(dict.lookup("東京都").get(0));
+
+        List<Morpheme> splits = tokenizer.split(morphemes, Tokenizer.SplitMode.A);
+        assertThat(splits.size(), is(3));
+        assertThat(splits.get(0).normalizedForm(), is("京都"));
+        assertThat(splits.get(1).normalizedForm(), is("東京"));
+        assertThat(splits.get(2).normalizedForm(), is("都"));
+    }
+
+    @Test
+    public void splitMixedMorphemeList() {
+        List<Morpheme> morphemes = new ArrayList<>();
+        for (Morpheme m : tokenizer.tokenize(Tokenizer.SplitMode.C, "な。な")) {
+            morphemes.add(m);
+        }
+        morphemes.add(dict.lookup("東京都").get(0));
+
+        List<Morpheme> splits = tokenizer.split(morphemes, Tokenizer.SplitMode.A);
+        assertThat(splits.size(), is(3));
+        assertThat(splits.get(0).normalizedForm(), is("アイウ"));
+        assertThat(splits.get(2).normalizedForm(), is("都"));
+    }
+
     @Test
     public void dumpInternalStructures() {
         String json = tokenizer.dumpInternalStructures("東京都");