diff --git a/packages/frontend/assets/room/objects/books/books.blend b/packages/frontend/assets/room/objects/books/books.blend
index 1a44ec676e..2d9fb150d1 100644
Binary files a/packages/frontend/assets/room/objects/books/books.blend and b/packages/frontend/assets/room/objects/books/books.blend differ
diff --git a/packages/frontend/assets/room/objects/books/books.glb b/packages/frontend/assets/room/objects/books/books.glb
index a820d4f96f..7ef2e6cb4e 100644
Binary files a/packages/frontend/assets/room/objects/books/books.glb and b/packages/frontend/assets/room/objects/books/books.glb differ
diff --git a/packages/frontend/src/utility/room/engine.ts b/packages/frontend/src/utility/room/engine.ts
index 9350784b05..9c88947b03 100644
--- a/packages/frontend/src/utility/room/engine.ts
+++ b/packages/frontend/src/utility/room/engine.ts
@@ -103,6 +103,8 @@ type ObjectDef<OpSc extends OptionsSchema = OptionsSchema> = {
 		default: GetOptionsSchemaValues<OpSc>;
 	};
 	placement: 'top' | 'side' | 'bottom' | 'wall' | 'ceiling' | 'floor';
+	//groupingMeshes: string[]; // multi-materialなメッシュは複数のメッシュに分割されるが、それだと不便な場合に追加の親メッシュでグルーピングするための指定
+	mergeMeshes?: string[] | null; // multi-materialなメッシュは複数のメッシュに分割されるが、それだと不便な場合にメッシュをマージするための指定
 	isChair?: boolean;
 	createInstance: (args: {
 		room: RoomEngine;
@@ -793,6 +795,20 @@ export class RoomEngine {
 
 		const loaderResult = await BABYLON.ImportMeshAsync(`/client-assets/room/objects/${camelToKebab(args.type)}/${camelToKebab(args.type)}.glb`, this.scene);
 
+		// babylonによって自動で追加される右手系変換用ノード
+		const subRoot = loaderResult.meshes[0];
+		subRoot.scaling = subRoot.scaling.scale(WORLD_SCALE);// cmをmに
+
+		if (def.mergeMeshes != null) {
+			for (const groupingMeshKeyword of def.mergeMeshes) {
+				const meshes = loaderResult.meshes.filter(m => m.name.includes(groupingMeshKeyword));
+				const merged = BABYLON.Mesh.MergeMeshes(meshes as BABYLON.Mesh[], true, true, undefined, false, true);
+				merged.name = `${groupingMeshKeyword}.grouped`;
+				merged.setParent(subRoot);
+				loaderResult.meshes.push(merged);
+			}
+		}
+
 		let hasCollisionMesh = false;
 		for (const mesh of loaderResult.meshes) {
 			if (mesh.name.includes('__COLLISION__')) {
@@ -808,10 +824,6 @@ export class RoomEngine {
 			isCollision: !hasCollisionMesh,
 		};
 
-		// babylonによって自動で追加される右手系変換用ノード
-		const subRoot = loaderResult.meshes[0];
-		subRoot.scaling = subRoot.scaling.scale(WORLD_SCALE);// cmをmに
-
 		root.addChild(subRoot);
 
 		root.position = args.position.clone();
@@ -1071,20 +1083,35 @@ export class RoomEngine {
 
 		const materials = new WeakMap<BABYLON.Material, BABYLON.Material>();
 
-		for (const m of ghost.getChildMeshes()) {
+		for (const m of ghost.getChildMeshes() as BABYLON.Mesh[]) {
 			m.metadata = { isGhost: true };
 			m.checkCollisions = false;
 
-			if (m.material) {
-				if (materials.has(m.material)) {
-					m.material = materials.get(m.material)!;
-				} else {
-					const mat = m.material.clone(`${m.material.name}_ghost`);
-					mat.alpha = 0.3;
-					mat.transparencyMode = BABYLON.Material.MATERIAL_ALPHABLEND;
-					materials.set(m.material, mat);
-					m.material = mat;
+			if (m.material == null) continue;
+
+			if (materials.has(m.material)) {
+				m.material = materials.get(m.material)!;
+				continue;
+			}
+
+			if (m.subMeshes != null && m.subMeshes.length > 0 && m.material.subMaterials != null) {
+				const multiGhostMaterial = m.material.clone(`${m.material.name}_ghost`) as BABYLON.MultiMaterial;
+
+				for (let i = 0; i < multiGhostMaterial.subMaterials.length; i++) {
+					const subMaterial = multiGhostMaterial.subMaterials[i];
+					const ghostMaterial = subMaterial.clone(`${subMaterial.name}_ghost`);
+					ghostMaterial.alpha = 0.3;
+					ghostMaterial.transparencyMode = BABYLON.Material.MATERIAL_ALPHABLEND;
+					multiGhostMaterial.subMaterials[i] = ghostMaterial;
+					materials.set(m.material, multiGhostMaterial);
+					m.material = multiGhostMaterial;
 				}
+			} else {
+				const ghostMaterial = m.material.clone(`${m.material.name}_ghost`);
+				ghostMaterial.alpha = 0.3;
+				ghostMaterial.transparencyMode = BABYLON.Material.MATERIAL_ALPHABLEND;
+				materials.set(m.material, ghostMaterial);
+				m.material = ghostMaterial;
 			}
 		}
 
diff --git a/packages/frontend/src/utility/room/objects/books.ts b/packages/frontend/src/utility/room/objects/books.ts
index 6afad2dcdb..61b49c9095 100644
--- a/packages/frontend/src/utility/room/objects/books.ts
+++ b/packages/frontend/src/utility/room/objects/books.ts
@@ -13,7 +13,28 @@ export const books = defineObject({
 		default: {},
 	},
 	placement: 'top',
-	createInstance: () => {
+	mergeMeshes: ['__X_BOOK_1__', '__X_BOOK_2__', '__X_BOOK_3__', '__X_BOOK_4__', '__X_BOOK_5__', '__X_BOOK_6__', '__X_BOOK_7__', '__X_BOOK_8__', '__X_BOOK_9__', '__X_BOOK_10__'],
+	createInstance: ({ findMesh, root }) => {
+		console.log(root.getChildMeshes().map((m) => m.name));
+
+		const bookMeshes = [
+			findMesh('__X_BOOK_1__'),
+			findMesh('__X_BOOK_2__'),
+			findMesh('__X_BOOK_3__'),
+			findMesh('__X_BOOK_4__'),
+			findMesh('__X_BOOK_5__'),
+			findMesh('__X_BOOK_6__'),
+			findMesh('__X_BOOK_7__'),
+			findMesh('__X_BOOK_8__'),
+			findMesh('__X_BOOK_9__'),
+			findMesh('__X_BOOK_10__'),
+		];
+
+		for (const mesh of bookMeshes) {
+			mesh.position.z -= Math.random() * 0.005/*cm*/;
+			mesh.position.y += Math.random() * 0.0025/*cm*/;
+		}
+
 		return {
 			interactions: {},
 		};