diff --git a/backend/lib/romaji.js b/backend/lib/romaji.js
index 672e987..41f4670 100644
--- a/backend/lib/romaji.js
+++ b/backend/lib/romaji.js
@@ -65,12 +65,16 @@ function _hiraToRomaji(str) {
 
 const JP_RE = /[぀-ヿ㐀-䶿一-鿿＀-￯]/;
 
+const KATA_RE = /[ァ-ヶ]/;
+
 function toRomaji(text) {
   if (!text || !_tokenizer || !JP_RE.test(text)) return text || '';
   const tokens = _tokenizer.tokenize(text);
   const hira = tokens.map(t => {
     const r = t.reading;
-    return (r && r !== '*') ? _kataToHira(r) : t.surface_form;
+    if (r && r !== '*') return _kataToHira(r);
+    if (KATA_RE.test(t.surface_form)) return _kataToHira(t.surface_form); // katakana proper noun
+    return t.surface_form;
   }).join('');
   return _hiraToRomaji(hira).toLowerCase();
 }
@@ -81,7 +85,10 @@ function romajiForStorage(text) {
   const tokens = _tokenizer.tokenize(text);
   const parts = tokens.map(t => {
     const r = t.reading;
-    if (!r || r === '*') return t.surface_form; // ASCII — keep original
+    if (!r || r === '*') {
+      if (KATA_RE.test(t.surface_form)) return _hiraToRomaji(_kataToHira(t.surface_form)); // katakana proper noun
+      return t.surface_form; // ASCII — keep original
+    }
     return _hiraToRomaji(_kataToHira(r));        // Japanese — convert (lowercase)
   });
   // Add space between adjacent alphabetic segments (word separation for names/titles)
diff --git a/src/ui.js b/src/ui.js
index afbd317..7d1e258 100644
--- a/src/ui.js
+++ b/src/ui.js
@@ -364,10 +364,13 @@ export function toggleInfoEdit() {
   fetchRomajiIndex().catch(() => null).then(() => {
     const rm = romajiLookup(_sId);
     if (rm) {
-      document.getElementById('ie-titlesort').value       = rm.titleRomaji  || '';
-      document.getElementById('ie-artistsort').value      = rm.artistRomaji || '';
-      document.getElementById('ie-albumartistsort').value = rm.artistRomaji || '';
-      document.getElementById('ie-albumsort').value       = rm.albumRomaji  || '';
+      const _jp = /[ぁ-んァ-ン一-龯]/;
+      if (rm.titleRomaji  && !_jp.test(rm.titleRomaji))  document.getElementById('ie-titlesort').value       = rm.titleRomaji;
+      if (rm.artistRomaji && !_jp.test(rm.artistRomaji)) {
+        document.getElementById('ie-artistsort').value      = rm.artistRomaji;
+        document.getElementById('ie-albumartistsort').value = rm.artistRomaji;
+      }
+      if (rm.albumRomaji  && !_jp.test(rm.albumRomaji))  document.getElementById('ie-albumsort').value       = rm.albumRomaji;
     }
     if (!S.cfg.backendUrl || !_sId) return null;
     const p = new URLSearchParams({ ndUrl: S.cfg.url, user: S.cfg.user, pass: S.cfg.pass, songId: _sId });