diff --git a/src/mnemonic/mnemonic.py b/src/mnemonic/mnemonic.py
index caa4ffb..3613bdd 100644
--- a/src/mnemonic/mnemonic.py
+++ b/src/mnemonic/mnemonic.py
@@ -152,7 +152,7 @@ def generate(self, strength: int = 128) -> str:
     # Adapted from <http://tinyurl.com/oxmn476>
     def to_entropy(self, words: list[str] | str) -> bytearray:
         if not isinstance(words, list):
-            words = words.split(" ")
+            words = self.normalize_string(words).split()
         if len(words) not in [12, 15, 18, 21, 24]:
             raise ValueError(
                 "Number of words must be one of the following: [12, 15, 18, 21, 24], but it is not (%d)."
@@ -210,7 +210,7 @@ def to_mnemonic(self, data: bytes) -> str:
         return self.delimiter.join(result)
 
     def check(self, mnemonic: str) -> bool:
-        mnemonic_list = self.normalize_string(mnemonic).split(" ")
+        mnemonic_list = self.normalize_string(mnemonic).split()
         # list of valid mnemonic lengths
         if len(mnemonic_list) not in [12, 15, 18, 21, 24]:
             return False
@@ -241,11 +241,11 @@ def expand_word(self, prefix: str) -> str:
                 return prefix
 
     def expand(self, mnemonic: str) -> str:
-        return " ".join(map(self.expand_word, mnemonic.split(" ")))
+        return " ".join(map(self.expand_word, mnemonic.split()))
 
     @classmethod
     def to_seed(cls, mnemonic: str, passphrase: str = "") -> bytes:
-        mnemonic = cls.normalize_string(mnemonic)
+        mnemonic = " ".join(cls.normalize_string(mnemonic).split())
         passphrase = cls.normalize_string(passphrase)
         passphrase = "mnemonic" + passphrase
         mnemonic_bytes = mnemonic.encode("utf-8")
diff --git a/tests/test_mnemonic.py b/tests/test_mnemonic.py
index 641cf16..3d13c0a 100755
--- a/tests/test_mnemonic.py
+++ b/tests/test_mnemonic.py
@@ -141,6 +141,38 @@ def test_expand_word(self) -> None:
             "action", m.expand_word("acti")
         )  # unique prefix expanded to word in list
 
+    def test_japanese_vectors_to_entropy(self) -> None:
+        # the ideographic space separates words on every path, not only in
+        # to_mnemonic; see #110, whose fix split on self.delimiter and was
+        # reverted because NFKD had already turned U+3000 into a space
+        with open("vectors.json", "r") as f:
+            vectors = json.load(f)
+        m = Mnemonic("japanese")
+        for v in vectors["japanese"]:
+            self.assertIn("\u3000", v[1])
+            entropy = bytes(m.to_entropy(v[1]))
+            self.assertEqual(v[0], entropy.hex())
+            self.assertEqual(v[1], m.to_mnemonic(entropy))
+
+    def test_whitespace_runs(self) -> None:
+        # check(), to_entropy() and to_seed() read the same separator: any
+        # run of unicode whitespace, once NFKD has been applied
+        m = Mnemonic("english")
+        canonical = "abandon " * 11 + "about"
+        entropy = m.to_entropy(canonical)
+        seed = Mnemonic.to_seed(canonical)
+        for variant in (
+            " " + canonical,
+            canonical + "\n",
+            canonical.replace("abandon about", "abandon  about"),
+            canonical.replace(" ", "\t"),
+            canonical.replace(" ", "\u3000"),
+            canonical.replace(" ", "\u00a0"),
+        ):
+            self.assertIs(m.check(variant), True)
+            self.assertEqual(entropy, m.to_entropy(variant))
+            self.assertEqual(seed, Mnemonic.to_seed(variant))
+
     def test_expand(self) -> None:
         m = Mnemonic("english")
         self.assertEqual("access", m.expand("access"))