diff --git a/scripts/convert_zh.py b/scripts/convert_zh.py
index 3fe7852a..8871e9b8 100755
--- a/scripts/convert_zh.py
+++ b/scripts/convert_zh.py
@@ -1,11 +1,12 @@
 #!/usr/bin/env python3
+import difflib
 import os
 from pathlib import Path
 from subprocess import check_output
 
 import opencc
 from hypy_utils import write
-from hypy_utils.tqdm_utils import pmap
+from hypy_utils.tqdm_utils import pmap, smap
 
 ALLOWED_DIRS = {Path(p) for p in ['people']}
 ALLOWED_SUF = {'.json5', '.md'}
@@ -15,6 +16,7 @@ HANS_TO_HANT = opencc.OpenCC('s2t.json')
 D_SELF = Path(__file__).parent
 D_PAST = D_SELF / '.convert_past'
 D_LAST_HASH = D_PAST / 'last-hash.txt'
+LAST_HASH = D_LAST_HASH.read_text().strip()
 
 
 def list_files() -> set[Path]:
@@ -30,27 +32,126 @@ def list_files() -> set[Path]:
     return files
 
 
+def inline_diff(old: str, new: str) -> tuple[list[str], list[str], list[tuple[str, str]]]:
+    matcher = difflib.SequenceMatcher(None, old, new)
+
+    a: list[str] = []
+    d: list[str] = []
+    r: list[tuple[str, str]] = []
+
+    def find_change(tag, s0, e0, s1, e1):
+        # Tag can be replace, delete, insert, equal
+        if tag == 'replace':
+            r.append((old[s0:e0], new[s1:e1]))
+        if tag == 'delete':
+            d.append(old[s0:e0])
+        if tag == 'insert':
+            a.append(new[s1:e1])
+
+    for t in matcher.get_opcodes():
+        find_change(*t)
+
+    return a, d, r
+
+
+def inline_diff_apply(old: str, new: str, alt: str) -> str:
+    """
+    Apply inline diff between two strings to an alternative string
+
+    Changes between new and old will be applied to alt, while changes in alt will not be removed.
+
+    :param old: Old string
+    :param new: New string
+    :param alt: Old alternative string to apply to
+    :return: New alternative string
+    """
+    # Find differences between old and new
+    a, d, r = inline_diff(old, new)
+
+    # Find differences between alt and new, apply differences that are present between old and new
+    matcher = difflib.SequenceMatcher(None, alt, new)
+    inc = 0
+
+    for tag, s0, e0, s1, e1 in matcher.get_opcodes():
+        s0 += inc
+        e0 += inc
+
+        # Tag can be replace, delete, insert, equal
+        if tag == 'replace':
+            df = (alt[s0:e0], new[s1:e1])
+            if df not in r:
+                continue
+
+            print(f'[Diff] Applying [U] {repr(df)}')
+            alt = alt[:s0] + new[s1:e1] + alt[e0:]
+            inc += (e1 - s1) - (e0 - s0)
+
+        if tag == 'delete':
+            if alt[s0:e0] not in d:
+                continue
+
+            print(f'[Diff] Applying [-] {repr(alt[s0:e0])}')
+            alt = alt[:s0] + alt[e0:]
+            inc -= e0 - s0
+
+        if tag == 'insert':
+            if new[s1:e1] not in a:
+                continue
+
+            print(f'[Diff] Applying [+] {repr(new[s1:e1])}')
+            alt = alt[:s0] + new[s1:e1] + alt[s0:]
+            inc += e1 - s1
+
+    return alt
+
+
 def process_file(f: Path):
     if '.zh_hant.' in f.name:
         return
 
+    hans = f.read_text()
+    converted = HANS_TO_HANT.convert(hans)
     f_hant = f.with_name(f'{f.stem}.zh_hant{f.suffix}')
 
     if not f_hant.is_file():
         # If hant file doesn't exist, create
-        f_hant.write_text(HANS_TO_HANT.convert(f.read_text()))
+        f_hant.write_text(converted)
 
     else:
-        # TODO
-        pass
+        hant_current = f_hant.read_text()
+
+        # Hant file exists, use diff
+        # Obtain original version from git
+        past = check_output(['git', 'show', f"{LAST_HASH}:{f.relative_to('.')}"]).decode()
+
+        # Nothing changed, skip
+        if past == hans:
+            return
+
+        print(f"\n============ CHANGED FILE: {f} ============")
+        print("> Trying to apply diff...")
+
+        # Diff: Obtain a list of inline differences from the HANS change (converted to HANT)
+        a, d, r = inline_diff(HANS_TO_HANT.convert(past), converted)
+        print('> Diff from old to new:', a, d, r)
+
+        a, d, r = inline_diff(hant_current, converted)
+        print('> Diff from hant to new:', a, d, r)
+
+        hant_new = inline_diff_apply(HANS_TO_HANT.convert(past), converted, hant_current)
+        f_hant.write_text(hant_new)
+
+        a, d, r = inline_diff(hant_new, converted)
+        print('> Diff from hant_new to new:', a, d, r)
+        print(f"============ DONE ============")
 
 
 if __name__ == '__main__':
     # Process files
-    pmap(process_file, list_files())
+    smap(process_file, list_files())
 
     # Write last hash
-    last_commit = check_output(['git', 'rev-parse', 'HEAD'])
+    last_commit = check_output(['git', 'rev-parse', 'HEAD']).decode()
     write(D_LAST_HASH, last_commit)
 
     print('Done')