diff --git a/packages/server/src/route/comic.ts b/packages/server/src/route/comic.ts
index 23ac39c..6b30b0b 100644
--- a/packages/server/src/route/comic.ts
+++ b/packages/server/src/route/comic.ts
@@ -3,71 +3,13 @@ import Router from "koa-router";
 import { createReadableStreamFromZip, entriesByNaturalOrder, readZip } from "../util/zipwrap.ts";
 import type { ContentContext } from "./context.ts";
 import { since_last_modified } from "./util.ts";
-import type { ZipReader } from "@zip.js/zip.js";
-import type { FileHandle } from "node:fs/promises";
 import { Readable } from "node:stream";
 
-/**
- * zip stream cache.
- */
-const ZipStreamCache = new Map<string, {
-	reader: ZipReader<FileHandle>,
-	refCount: number,
-}>();
-
-
-function markUseZip(path: string) {
-	const ret = ZipStreamCache.get(path);
-	if (ret) {
-		ret.refCount++;
-	}
-	return ret !== undefined;
-}
-
-async function acquireZip(path: string, marked = false) {
-	const ret = ZipStreamCache.get(path);
-	if (!ret) {
-		const obj = await readZip(path);
-		const check = ZipStreamCache.get(path);
-		if (check) {
-			check.refCount++;
-			// if the cache is updated, release the previous one.
-			releaseZip(path);
-			return check.reader;
-		}
-		// if the cache is not updated, set the new one.
-		ZipStreamCache.set(path, {
-			reader: obj.reader,
-			refCount: 1,
-		});
-		return obj.reader;
-	}
-	if (!marked) {
-		ret.refCount++;
-	}
-	return ret.reader;
-}
-
-function releaseZip(path: string) {
-	const obj = ZipStreamCache.get(path);
-	if (obj === undefined) {
-		console.warn(`warning! duplicate release at ${path}`);
-		return;
-	}
-	if (obj.refCount === 1) {
-		const { reader } = obj;
-		reader.close();
-		ZipStreamCache.delete(path);
-	} else {
-		obj.refCount--;
-	}
-}
 
 async function renderZipImage(ctx: Context, path: string, page: number) {
 	const image_ext = ["gif", "png", "jpeg", "bmp", "webp", "jpg", "avif"];
-	const marked = markUseZip(path);
-	const zip = await acquireZip(path, marked);
-	const entries = (await entriesByNaturalOrder(zip)).filter((x) => {
+	const zip = await readZip(path);
+	const entries = (await entriesByNaturalOrder(zip.reader)).filter((x) => {
 		const ext = x.filename.split(".").pop();
 		return ext !== undefined && image_ext.includes(ext);
 	});
@@ -77,7 +19,7 @@ async function renderZipImage(ctx: Context, path: string, page: number) {
 		if (since_last_modified(ctx, last_modified)) {
 			return;
 		}
-		const read_stream = await createReadableStreamFromZip(zip, entry);
+		const read_stream = await createReadableStreamFromZip(zip.reader, entry);
 		const nodeReadableStream = new Readable();
 		nodeReadableStream._read = () => { };
 
@@ -91,14 +33,13 @@ async function renderZipImage(ctx: Context, path: string, page: number) {
 		}));
 		nodeReadableStream.on("error", (err) => {
 			console.error("readalbe stream error",err);
-			setTimeout(()=>{
-				releaseZip(path)
-			},100);
+			ctx.status = 500;
+			ctx.body = "Internal Server Error";
+			zip.reader.close();
+			return;
 		});
 		nodeReadableStream.on("close", () => {
-			setTimeout(()=>{
-			releaseZip(path);
-			},100);
+			zip.reader.close();
 		});
 
 		ctx.body = nodeReadableStream;
diff --git a/packages/server/src/util/zipwrap.ts b/packages/server/src/util/zipwrap.ts
index 30facc0..5f0ece2 100644
--- a/packages/server/src/util/zipwrap.ts
+++ b/packages/server/src/util/zipwrap.ts
@@ -21,6 +21,7 @@ class FileReader extends Reader<string> {
 		// not implemented yet
 		(this.fd as unknown as EventEmitter).on("close", () => {
 			console.warn(`file handle closed: ${this.path}`);
+			this.fd?.close();
 			this.fd = undefined;
 		});
 	}