diff --git a/packages/backend/src/core/MahjongService.ts b/packages/backend/src/core/MahjongService.ts
index ca8c2f685e..98803590e6 100644
--- a/packages/backend/src/core/MahjongService.ts
+++ b/packages/backend/src/core/MahjongService.ts
@@ -657,8 +657,7 @@ export class MahjongService implements OnApplicationShutdown, OnModuleInit {
 
 		if (mj.riichis[house]) {
 			// リーチ時はアガリ牌でない限りツモ切り
-			const horaSets = Mmj.getHoraSets(mj.handTileTypes[house]);
-			if (horaSets.length === 0) {
+			if (!Mmj.canHora(mj.handTileTypes[house])) {
 				setTimeout(() => {
 					this.dahai(room, mj, house, mj.handTiles[house].at(-1));
 				}, 500);
diff --git a/packages/frontend/src/pages/mahjong/room.game.vue b/packages/frontend/src/pages/mahjong/room.game.vue
index a0d50c3330..7de89858ad 100644
--- a/packages/frontend/src/pages/mahjong/room.game.vue
+++ b/packages/frontend/src/pages/mahjong/room.game.vue
@@ -292,7 +292,7 @@ const isMyTurn = computed(() => {
 });
 
 const canHora = computed(() => {
-	return Mmj.getHoraSets(mj.value.myHandTileTypes).length > 0;
+	return Mmj.canHora(mj.value.myHandTileTypes).length;
 });
 
 const selectableTiles = ref<Mmj.TileType[] | null>(null);
diff --git a/packages/misskey-mahjong/src/common.ts b/packages/misskey-mahjong/src/common.ts
index 63314e522d..2278a2e81f 100644
--- a/packages/misskey-mahjong/src/common.ts
+++ b/packages/misskey-mahjong/src/common.ts
@@ -237,6 +237,8 @@ export const PREV_TILE_FOR_SHUNTSU: Record<TileType, TileType | null> = {
 	chun: null,
 };
 
+const KOKUSHI_TILES: TileType[] = ['m1', 'm9', 'p1', 'p9', 's1', 's9', 'e', 's', 'w', 'n', 'haku', 'hatsu', 'chun'];
+
 type EnvForCalcYaku = {
 	house: House;
 
@@ -471,7 +473,7 @@ export const YAKU_DEFINITIONS = [{
 
 		// TODO: 両面待ちかどうか
 
-		const horaSets = getHoraSets(state.handTiles.concat(state.tsumoTile ?? state.ronTile));
+		const horaSets = analyze1head3mentsuSets(state.handTiles.concat(state.tsumoTile ?? state.ronTile));
 		return horaSets.some(horaSet => {
 			// 風牌判定(役牌でなければOK)
 			if (horaSet.head === state.seatWind) return false;
@@ -489,7 +491,7 @@ export const YAKU_DEFINITIONS = [{
 		// 面前じゃないとダメ
 		if (state.huros.some(huro => CALL_HURO_TYPES.includes(huro.type))) return false;
 
-		const horaSets = getHoraSets(state.handTiles.concat(state.tsumoTile ?? state.ronTile));
+		const horaSets = analyze1head3mentsuSets(state.handTiles.concat(state.tsumoTile ?? state.ronTile));
 		return horaSets.some(horaSet => {
 			// 同じ順子が2つあるか？
 			return horaSet.mentsus.some((mentsu) =>
@@ -505,12 +507,26 @@ export const YAKU_DEFINITIONS = [{
 		if (state.huros.length > 0) {
 			if (state.huros.some(huro => huro.type === 'cii')) return false;
 		}
-		const horaSets = getHoraSets(state.handTiles.concat(state.tsumoTile ?? state.ronTile));
+		const horaSets = analyze1head3mentsuSets(state.handTiles.concat(state.tsumoTile ?? state.ronTile));
 		return horaSets.some(horaSet => {
 			// 全て刻子か？
 			if (!horaSet.mentsus.every((mentsu) => mentsu[0] === mentsu[1])) return false;
 		});
 	},
+}, {
+	name: 'chitoitsu',
+	fan: 2,
+	isYakuman: false,
+	calc: (state: EnvForCalcYaku) => {
+		return isChitoitsu(state.handTiles.concat(state.tsumoTile ?? state.ronTile));
+	},
+}, {
+	name: 'kokushi',
+	fan: 13,
+	isYakuman: true,
+	calc: (state: EnvForCalcYaku) => {
+		return isKokushi(state.handTiles.concat(state.tsumoTile ?? state.ronTile));
+	},
 }];
 
 export function fanToPoint(fan: number, isParent: boolean): number {
@@ -709,7 +725,7 @@ function extractShuntsus(tiles: TileType[]): [TileType, TileType, TileType][] {
  * @param handTiles ポン、チー、カンした牌を含まない手牌
  * @returns
  */
-export function getHoraSets(handTiles: TileType[]): HoraSet[] {
+function analyze1head3mentsuSets(handTiles: TileType[]): HoraSet[] {
 	const horaSets: HoraSet[] = [];
 
 	const headSet: TileType[] = [];
@@ -808,6 +824,14 @@ export function getHoraSets(handTiles: TileType[]): HoraSet[] {
 	return horaSets;
 }
 
+export function canHora(handTiles: TileType[]): boolean {
+	if (isKokushi(handTiles)) return true;
+	if (isChitoitsu(handTiles)) return true;
+
+	const horaSets = analyze1head3mentsuSets(handTiles);
+	return horaSets.length > 0;
+}
+
 /**
  * アガリ牌リストを取得
  * @param handTiles ポン、チー、カンした牌を含まない手牌
@@ -815,14 +839,23 @@ export function getHoraSets(handTiles: TileType[]): HoraSet[] {
 export function getHoraTiles(handTiles: TileType[]): TileType[] {
 	return TILE_TYPES.filter(tile => {
 		const tempHandTiles = [...handTiles, tile];
-		const horaSets = getHoraSets(tempHandTiles);
+		const horaSets = analyze1head3mentsuSets(tempHandTiles);
 		return horaSets.length > 0;
 	});
 }
 
-// TODO: 国士無双判定関数
+function isKokushi(handTiles: TileType[]): boolean {
+	return KOKUSHI_TILES.every(t => handTiles.includes(t));
+}
 
-// TODO: 七対子判定関数
+function isChitoitsu(handTiles: TileType[]): boolean {
+	const countMap = new Map<TileType, number>();
+	for (const tile of handTiles) {
+		const count = (countMap.get(tile) ?? 0) + 1;
+		countMap.set(tile, count);
+	}
+	return Array.from(countMap.values()).every(c => c === 2);
+}
 
 export function getTilesForRiichi(handTiles: TileType[]): TileType[] {
 	return handTiles.filter(tile => {
diff --git a/packages/misskey-mahjong/src/engine.master.ts b/packages/misskey-mahjong/src/engine.master.ts
index e611e3bc00..8821192867 100644
--- a/packages/misskey-mahjong/src/engine.master.ts
+++ b/packages/misskey-mahjong/src/engine.master.ts
@@ -108,8 +108,7 @@ class StateManager {
 		// TODO: ポンされるなどして自分の河にない場合の考慮
 		if (this.hoTileTypes[house].includes($type(tid))) return false;
 
-		const horaSets = Common.getHoraSets(this.handTileTypes[house].concat($type(tid)));
-		if (horaSets.length === 0) return false; // 完成形じゃない
+		if (!Common.canHora(this.handTileTypes[house].concat($type(tid)))) return false; // 完成形じゃない
 
 		// TODO
 		//const yakus = YAKU_DEFINITIONS.filter(yaku => yaku.calc(this.state, { tsumoTile: null, ronTile: tile }));
diff --git a/packages/misskey-mahjong/src/engine.player.ts b/packages/misskey-mahjong/src/engine.player.ts
index 3e4fbdb894..d1a9094133 100644
--- a/packages/misskey-mahjong/src/engine.player.ts
+++ b/packages/misskey-mahjong/src/engine.player.ts
@@ -218,7 +218,7 @@ export class PlayerGameEngine {
 
 		if (house === this.myHouse) {
 		} else {
-			const canRon = Common.getHoraSets(this.myHandTiles.concat(tid).map(id => $type(id))).length > 0;
+			const canRon = Common.canHora(this.myHandTiles.concat(tid).map(id => $type(id)));
 			const canPon = !this.isMeRiichi && this.myHandTileTypes.filter(t => t === $type(tid)).length === 2;
 			const canKan = !this.isMeRiichi && this.myHandTileTypes.filter(t => t === $type(tid)).length === 3;
 			const canCii = !this.isMeRiichi && house === Common.prevHouse(this.myHouse) &&