diff --git a/packages/backend/src/core/MahjongService.ts b/packages/backend/src/core/MahjongService.ts
index 8957edd4e8..e4abbe8076 100644
--- a/packages/backend/src/core/MahjongService.ts
+++ b/packages/backend/src/core/MahjongService.ts
@@ -60,7 +60,7 @@ type Room = {
 
 type CallingAnswers = {
 	pon: null | boolean;
-	cii: null | false | [Mahjong.Tile, Mahjong.Tile, Mahjong.Tile];
+	cii: null | false | 'x__' | '_x_' | '__x';
 	kan: null | boolean;
 	ron: {
 		e: null | boolean;
@@ -594,7 +594,7 @@ export class MahjongService implements OnApplicationShutdown, OnModuleInit {
 	}
 
 	@bindThis
-	public async commit_cii(roomId: MiMahjongGame['id'], user: MiUser, tiles: [Mahjong.Tile, Mahjong.Tile, Mahjong.Tile]) {
+	public async commit_cii(roomId: MiMahjongGame['id'], user: MiUser, pattern: 'x__' | '_x_' | '__x') {
 		const room = await this.getRoom(roomId);
 		if (room == null) return;
 		if (room.gameState == null) return;
@@ -605,7 +605,7 @@ export class MahjongService implements OnApplicationShutdown, OnModuleInit {
 		const current = await this.redisClient.get(`mahjong:gameCallingAsking:${room.id}`);
 		if (current == null) throw new Error('no asking found');
 		const currentAnswers = JSON.parse(current) as CallingAnswers;
-		currentAnswers.cii = tiles;
+		currentAnswers.cii = pattern;
 		await this.redisClient.set(`mahjong:gameCallingAsking:${room.id}`, JSON.stringify(currentAnswers));
 	}
 
diff --git a/packages/backend/src/server/api/stream/channels/mahjong-room.ts b/packages/backend/src/server/api/stream/channels/mahjong-room.ts
index 53363bd5f3..b2e2ccdb92 100644
--- a/packages/backend/src/server/api/stream/channels/mahjong-room.ts
+++ b/packages/backend/src/server/api/stream/channels/mahjong-room.ts
@@ -56,7 +56,7 @@ class MahjongRoomChannel extends Channel {
 			case 'tsumoHora': this.tsumoHora(); break;
 			case 'ronHora': this.ronHora(); break;
 			case 'pon': this.pon(); break;
-			case 'cii': this.cii(body.tiles); break;
+			case 'cii': this.cii(body.pattern); break;
 			case 'kan': this.kan(); break;
 			case 'ankan': this.ankan(body.tile); break;
 			case 'kakan': this.kakan(body.tile); break;
@@ -122,10 +122,10 @@ class MahjongRoomChannel extends Channel {
 	}
 
 	@bindThis
-	private async cii(tiles: string[]) {
+	private async cii(pattern: string) {
 		if (this.user == null) return;
 
-		this.mahjongService.commit_cii(this.roomId!, this.user, tiles);
+		this.mahjongService.commit_cii(this.roomId!, this.user, pattern);
 	}
 
 @bindThis
diff --git a/packages/frontend/assets/mahjong/tiles/chun.png b/packages/frontend/assets/mahjong/tiles/chun.png
index 819efe989e..5d57fcc4ab 100644
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diff --git a/packages/frontend/assets/mahjong/tiles/e.png b/packages/frontend/assets/mahjong/tiles/e.png
index bd6b0675ad..0443b5046d 100644
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diff --git a/packages/frontend/assets/mahjong/tiles/hatsu.png b/packages/frontend/assets/mahjong/tiles/hatsu.png
index c09cf8e62a..6481e5d2ec 100644
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diff --git a/packages/frontend/assets/mahjong/tiles/m1.png b/packages/frontend/assets/mahjong/tiles/m1.png
index de856fc358..a514dd3df0 100644
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diff --git a/packages/frontend/assets/mahjong/tiles/m2.png b/packages/frontend/assets/mahjong/tiles/m2.png
index a3a21ed398..5499cc3660 100644
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diff --git a/packages/frontend/assets/mahjong/tiles/m3.png b/packages/frontend/assets/mahjong/tiles/m3.png
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diff --git a/packages/frontend/assets/mahjong/tiles/m5.png b/packages/frontend/assets/mahjong/tiles/m5.png
index c3c008f865..0f088c9893 100644
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diff --git a/packages/frontend/assets/mahjong/tiles/m6.png b/packages/frontend/assets/mahjong/tiles/m6.png
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diff --git a/packages/frontend/assets/mahjong/tiles/m7.png b/packages/frontend/assets/mahjong/tiles/m7.png
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diff --git a/packages/frontend/assets/mahjong/tiles/m8.png b/packages/frontend/assets/mahjong/tiles/m8.png
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diff --git a/packages/frontend/assets/mahjong/tiles/m9.png b/packages/frontend/assets/mahjong/tiles/m9.png
index 690698fc01..1577fd2139 100644
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diff --git a/packages/frontend/assets/mahjong/tiles/n.png b/packages/frontend/assets/mahjong/tiles/n.png
index 9683db7a43..9ab59fef2e 100644
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diff --git a/packages/frontend/assets/mahjong/tiles/p1.png b/packages/frontend/assets/mahjong/tiles/p1.png
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diff --git a/packages/frontend/assets/mahjong/tiles/p2.png b/packages/frontend/assets/mahjong/tiles/p2.png
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diff --git a/packages/frontend/assets/mahjong/tiles/p5.png b/packages/frontend/assets/mahjong/tiles/p5.png
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diff --git a/packages/frontend/assets/mahjong/tiles/p6.png b/packages/frontend/assets/mahjong/tiles/p6.png
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diff --git a/packages/frontend/assets/mahjong/tiles/p7.png b/packages/frontend/assets/mahjong/tiles/p7.png
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diff --git a/packages/frontend/assets/mahjong/tiles/p9.png b/packages/frontend/assets/mahjong/tiles/p9.png
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diff --git a/packages/frontend/assets/mahjong/tiles/s1.png b/packages/frontend/assets/mahjong/tiles/s1.png
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diff --git a/packages/frontend/assets/mahjong/tiles/s3.png b/packages/frontend/assets/mahjong/tiles/s3.png
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diff --git a/packages/frontend/assets/mahjong/tiles/s4.png b/packages/frontend/assets/mahjong/tiles/s4.png
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diff --git a/packages/frontend/assets/mahjong/tiles/s5.png b/packages/frontend/assets/mahjong/tiles/s5.png
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diff --git a/packages/frontend/assets/mahjong/tiles/s7.png b/packages/frontend/assets/mahjong/tiles/s7.png
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diff --git a/packages/frontend/assets/mahjong/tiles/s8.png b/packages/frontend/assets/mahjong/tiles/s8.png
index 605f4cfe10..187cb89ceb 100644
Binary files a/packages/frontend/assets/mahjong/tiles/s8.png and b/packages/frontend/assets/mahjong/tiles/s8.png differ
diff --git a/packages/frontend/assets/mahjong/tiles/s9.png b/packages/frontend/assets/mahjong/tiles/s9.png
index c4c6246bf5..2c4134ecdb 100644
Binary files a/packages/frontend/assets/mahjong/tiles/s9.png and b/packages/frontend/assets/mahjong/tiles/s9.png differ
diff --git a/packages/frontend/assets/mahjong/tiles/w.png b/packages/frontend/assets/mahjong/tiles/w.png
index c18793b376..ac576f8a47 100644
Binary files a/packages/frontend/assets/mahjong/tiles/w.png and b/packages/frontend/assets/mahjong/tiles/w.png differ
diff --git a/packages/frontend/src/pages/mahjong/room.game.vue b/packages/frontend/src/pages/mahjong/room.game.vue
index dec7add7b2..99471d50da 100644
--- a/packages/frontend/src/pages/mahjong/room.game.vue
+++ b/packages/frontend/src/pages/mahjong/room.game.vue
@@ -781,7 +781,6 @@ onUnmounted(() => {
 	display: inline-block;
 	vertical-align: bottom;
 	width: 32px;
-	box-shadow: 0px 8px 2px 0px #0003;
 }
 
 .handTilesOfKamitya {
diff --git a/packages/misskey-mahjong/src/common.ts b/packages/misskey-mahjong/src/common.ts
index c4b1f7b97a..c0f44d4c1f 100644
--- a/packages/misskey-mahjong/src/common.ts
+++ b/packages/misskey-mahjong/src/common.ts
@@ -101,6 +101,80 @@ export const NEXT_TILE_FOR_DORA_MAP: Record<Tile, Tile> = {
 	chun: 'haku',
 };
 
+export const NEXT_TILE_FOR_SHUNTSU: Record<Tile, Tile | null> = {
+	m1: 'm2',
+	m2: 'm3',
+	m3: 'm4',
+	m4: 'm5',
+	m5: 'm6',
+	m6: 'm7',
+	m7: 'm8',
+	m8: 'm9',
+	m9: null,
+	p1: 'p2',
+	p2: 'p3',
+	p3: 'p4',
+	p4: 'p5',
+	p5: 'p6',
+	p6: 'p7',
+	p7: 'p8',
+	p8: 'p9',
+	p9: null,
+	s1: 's2',
+	s2: 's3',
+	s3: 's4',
+	s4: 's5',
+	s5: 's6',
+	s6: 's7',
+	s7: 's8',
+	s8: 's9',
+	s9: null,
+	e: null,
+	s: null,
+	w: null,
+	n: null,
+	haku: null,
+	hatsu: null,
+	chun: null,
+};
+
+export const PREV_TILE_FOR_SHUNTSU: Record<Tile, Tile | null> = {
+	m1: null,
+	m2: 'm1',
+	m3: 'm2',
+	m4: 'm3',
+	m5: 'm4',
+	m6: 'm5',
+	m7: 'm6',
+	m8: 'm7',
+	m9: 'm8',
+	p1: null,
+	p2: 'p1',
+	p3: 'p2',
+	p4: 'p3',
+	p5: 'p4',
+	p6: 'p5',
+	p7: 'p6',
+	p8: 'p7',
+	p9: 'p8',
+	s1: null,
+	s2: 's1',
+	s3: 's2',
+	s4: 's3',
+	s5: 's4',
+	s6: 's5',
+	s7: 's6',
+	s8: 's7',
+	s9: 's8',
+	e: null,
+	s: null,
+	w: null,
+	n: null,
+	haku: null,
+	hatsu: null,
+	chun: null,
+};
+
 type EnvForCalcYaku = {
 	house: House;
 
@@ -627,3 +701,27 @@ export function getTilesForRiichi(handTiles: Tile[]): Tile[] {
 export function nextTileForDora(tile: Tile): Tile {
 	return NEXT_TILE_FOR_DORA_MAP[tile];
 }
+
+export function getAvailableCiiPatterns(handTiles: Tile[], targetTile: Tile): [Tile, Tile, Tile][] {
+	const patterns: [Tile, Tile, Tile][] = [];
+	const prev1 = PREV_TILE_FOR_SHUNTSU[targetTile];
+	const prev2 = prev1 != null ? PREV_TILE_FOR_SHUNTSU[prev1] : null;
+	const next1 = NEXT_TILE_FOR_SHUNTSU[targetTile];
+	const next2 = next1 != null ? NEXT_TILE_FOR_SHUNTSU[next1] : null;
+	if (prev2 != null && prev1 != null) {
+		if (handTiles.includes(prev2) && handTiles.includes(prev1)) {
+			patterns.push([prev2, prev1, targetTile]);
+		}
+	}
+	if (prev1 != null && next1 != null) {
+		if (handTiles.includes(prev1) && handTiles.includes(next1)) {
+			patterns.push([prev1, targetTile, next1]);
+		}
+	}
+	if (next1 != null && next2 != null) {
+		if (handTiles.includes(next1) && handTiles.includes(next2)) {
+			patterns.push([targetTile, next1, next2]);
+		}
+	}
+	return patterns;
+}
diff --git a/packages/misskey-mahjong/src/engine.master.ts b/packages/misskey-mahjong/src/engine.master.ts
index 11992d877e..4bd436a2e3 100644
--- a/packages/misskey-mahjong/src/engine.master.ts
+++ b/packages/misskey-mahjong/src/engine.master.ts
@@ -436,7 +436,7 @@ export class MasterGameEngine {
 
 	public commit_resolveCallingInterruption(answers: {
 		pon: boolean;
-		cii: false | [Tile, Tile, Tile];
+		cii: false | 'x__' | '_x_' | '__x';
 		kan: boolean;
 		ron: House[];
 	}) {
@@ -497,9 +497,42 @@ export class MasterGameEngine {
 			};
 		} else if (cii != null && answers.cii) {
 			const tile = this.state.hoTiles[cii.callee].pop()!;
-			this.state.handTiles[cii.caller].splice(this.state.handTiles[cii.caller].indexOf(answers.cii[0]), 1);
-			this.state.handTiles[cii.caller].splice(this.state.handTiles[cii.caller].indexOf(answers.cii[1]), 1);
-			this.state.huros[cii.caller].push({ type: 'cii', tiles: [tile, answers.cii[0], answers.cii[1]], from: cii.callee });
+			let tiles: [Tile, Tile, Tile];
+
+			switch (answers.cii) {
+				case 'x__': {
+					const a = Common.NEXT_TILE_FOR_SHUNTSU[tile];
+					if (a == null) throw new Error();
+					const b = Common.NEXT_TILE_FOR_SHUNTSU[a];
+					if (b == null) throw new Error();
+					this.state.handTiles[cii.caller].splice(this.state.handTiles[cii.caller].indexOf(a), 1);
+					this.state.handTiles[cii.caller].splice(this.state.handTiles[cii.caller].indexOf(b), 1);
+					tiles = [tile, a, b];
+					break;
+				}
+				case '_x_': {
+					const a = Common.PREV_TILE_FOR_SHUNTSU[tile];
+					if (a == null) throw new Error();
+					const b = Common.NEXT_TILE_FOR_SHUNTSU[tile];
+					if (b == null) throw new Error();
+					this.state.handTiles[cii.caller].splice(this.state.handTiles[cii.caller].indexOf(a), 1);
+					this.state.handTiles[cii.caller].splice(this.state.handTiles[cii.caller].indexOf(b), 1);
+					tiles = [a, tile, b];
+					break;
+				}
+				case '__x': {
+					const a = Common.PREV_TILE_FOR_SHUNTSU[tile];
+					if (a == null) throw new Error();
+					const b = Common.PREV_TILE_FOR_SHUNTSU[a];
+					if (b == null) throw new Error();
+					this.state.handTiles[cii.caller].splice(this.state.handTiles[cii.caller].indexOf(a), 1);
+					this.state.handTiles[cii.caller].splice(this.state.handTiles[cii.caller].indexOf(b), 1);
+					tiles = [b, a, tile];
+					break;
+				}
+			}
+
+			this.state.huros[cii.caller].push({ type: 'cii', tiles: tiles, from: cii.callee });
 
 			this.state.turn = cii.caller;
 
@@ -507,7 +540,7 @@ export class MasterGameEngine {
 				type: 'ciied' as const,
 				caller: cii.caller,
 				callee: cii.callee,
-				tiles: [tile, answers.cii[0], answers.cii[1]],
+				tiles: tiles,
 				turn: this.state.turn,
 			};
 		} else if (this.state.tiles.length === 0) {