diff --git a/index.html b/index.html
index 6d4ed4d..f62f676 100644
--- a/index.html
+++ b/index.html
@@ -507,9 +507,9 @@ header{display:flex;align-items:center;justify-content:space-between;padding:0 1
               <i data-lucide="zap" style="width:13px;height:13px"></i>
               弱点集中特訓
             </div>
-            <button class="btn-sm" @click="exitWeakDrill()">
-              <i data-lucide="arrow-left" style="width:11px;height:11px"></i>
-              戻る
+            <button class="btn-sm" type="button" @click="exitWeakDrill()" aria-label="弱点特訓を終了する">
+              <i data-lucide="x" style="width:11px;height:11px"></i>
+              特訓をやめる
             </button>
           </div>
 
diff --git a/js/app.js b/js/app.js
index 7266c16..4aacfba 100644
--- a/js/app.js
+++ b/js/app.js
@@ -1,6 +1,10 @@
 /**
  * Alpine アプリ本体。単元データは ./data/categories.js と ./data/drills.js。
- * 表示系 HTML は safeHtml() 経由（DOMPurify）でサニタイズすること。
+ *
+ * HTML 方針:
+ * - マークアップを描画する箇所は x-html="safeHtml(...)" のみ。
+ * - タグを出さない一行表示には plainText(...)（サニタイズ後に textContent 化）。
+ * - 状態に保持する解説文字列は保存時に sanitizeStoredHtml で正規化。
  */
 import { DRILLS } from './data/drills.js';
 import { CATEGORIES } from './data/categories.js';
@@ -19,11 +23,27 @@ function sanitizeTrustedHtml(dirty) {
   });
 }
 
+/** localStorage / 画面状態に載せる HTML 断片の正規化（表示前と同じルール） */
+function sanitizeStoredHtml(html) {
+  return sanitizeTrustedHtml(html);
+}
+
+/** サニタイズ済み HTML からプレーン文字列（x-text 向け） */
+function plainTextFromSanitizedHtml(html) {
+  if (html == null || html === '') return '';
+  const d = document.createElement('div');
+  d.innerHTML = sanitizeTrustedHtml(String(html));
+  return (d.textContent || '').replace(/\s+/g, ' ').trim();
+}
+
 document.addEventListener('alpine:init', () => {
   Alpine.data('bokiApp', () => ({
     safeHtml(s) {
       return sanitizeTrustedHtml(s);
     },
+    plainText(s) {
+      return plainTextFromSanitizedHtml(s);
+    },
     categories:[],
     currentUnit:null,
     quizState:{},
@@ -228,7 +248,7 @@ document.addEventListener('alpine:init', () => {
     answered(qi){ return !!this.quizState[qi]; },
     doAnswer(qi,ci,correct,exp){
       if(this.quizState[qi]) return;
-      this.quizState[qi]={selected:ci,correct:ci===correct,exp};
+      this.quizState[qi]={selected:ci,correct:ci===correct,exp:sanitizeStoredHtml(exp)};
       this.quizState={...this.quizState};
       // Check if all questions answered
       const total=this.currentUnit?.quiz?.length||0;
@@ -353,7 +373,7 @@ document.addEventListener('alpine:init', () => {
     },
     doWeakDrillAnswer(qi,ci,correct,exp){
       if(this.weakDrillQuizState[qi]) return;
-      this.weakDrillQuizState[qi]={selected:ci,correct:ci===correct,exp};
+      this.weakDrillQuizState[qi]={selected:ci,correct:ci===correct,exp:sanitizeStoredHtml(exp)};
       this.weakDrillQuizState={...this.weakDrillQuizState};
     },
     get weakDrillAllAnswered(){
@@ -431,6 +451,7 @@ document.addEventListener('alpine:init', () => {
           this.resetFlashRevealState();
         }
       } else if(this.stepStep===3){
+        this.quizState={};
         const drills=this.unitDrills;
         if(drills.length>0){
           this.stepStep=2;
@@ -457,12 +478,16 @@ document.addEventListener('alpine:init', () => {
     },
     _kpDelimiterIndex(kp){
       if(!kp||typeof kp!=='string') return -1;
-      const iw=kp.indexOf('：');
-      const ia=kp.indexOf(':');
-      if(iw<0&&ia<0) return -1;
-      if(iw<0) return ia;
-      if(ia<0) return iw;
-      return Math.min(iw,ia);
+      const ja=kp.indexOf('：');
+      if(ja>=0) return ja;
+      let depth=0;
+      for(let i=0;i<kp.length;i++){
+        const ch=kp[i];
+        if(ch==='<') depth++;
+        else if(ch==='>') depth=Math.max(0,depth-1);
+        else if(ch===':'&&depth===0) return i;
+      }
+      return -1;
     },
     keypointHasFlip(idx){
       const kp=(this.currentUnit?.keypoints||[])[idx];
diff --git a/sw.js b/sw.js
index 6df9d67..aa7c8db 100644
--- a/sw.js
+++ b/sw.js
@@ -1,5 +1,5 @@
 // posimai-boki SW — stale-while-revalidate + skipWaiting
-const CACHE = 'posimai-boki-v15';
+const CACHE = 'posimai-boki-v16';
 const STATIC = ['/', '/index.html', '/manifest.json', '/logo.png', '/js/app.js', '/js/data/drills.js', '/js/data/categories.js'];
 
 self.addEventListener('install', e => {