diff --git a/src/content/manga.ts b/src/content/manga.ts
index 023ae0a..d9bbc2f 100644
--- a/src/content/manga.ts
+++ b/src/content/manga.ts
@@ -1,5 +1,5 @@
 import {ContentFile, createDefaultClass,registerContentReferrer, ContentConstructOption} from './file';
-import {readZip,createReadStreamFromZip, readAllFromZip} from '../util/zipwrap';
+import {readZip, readAllFromZip} from '../util/zipwrap';
 import { DocumentBody } from '../model/doc';
 import {extname} from 'path';
 
diff --git a/src/route/manga.ts b/src/route/manga.ts
index a7972e8..8515a7f 100644
--- a/src/route/manga.ts
+++ b/src/route/manga.ts
@@ -1,52 +1,103 @@
+import { Context, DefaultContext, DefaultState, Next } from "koa";
+import {
+  createReadableStreamFromZip,
+  entriesByNaturalOrder,
+  readZip,
+} from "../util/zipwrap";
+import { since_last_modified } from "./util";
+import { ContentContext } from "./context";
+import Router from "koa-router";
+import StreamZip from "node-stream-zip";
 
-import {Context, DefaultContext, DefaultState, Next} from 'koa';
-import {readZip,entriesByNaturalOrder,createReadStreamFromZip} from '../util/zipwrap';
-import {since_last_modified} from './util';
-import {ContentContext} from './context';
-import Router from 'koa-router';
+/**
+ * zip stream cache.
+ */
 
-async function renderZipImage(ctx: Context,path : string, page:number){
-    const image_ext = ['gif', 'png', 'jpeg', 'bmp', 'webp', 'jpg'];
-    let zip = await readZip(path);
-    const entries = entriesByNaturalOrder(zip).filter(x=>{
-        const ext = x.name.split('.').pop();
-        return ext !== undefined && image_ext.includes(ext);
+let ZipStreamCache: { [path: string]: [StreamZip, number] } = {};
+
+async function acquireZip(path: string) {
+  if (ZipStreamCache[path] === undefined) {
+    const ret = await readZip(path);
+    if (ZipStreamCache[path] === undefined) {
+      ZipStreamCache[path] = [ret, 1];
+      console.log(`acquire ${path} 1`);
+      return ret;
+    }
+    ret.close();
+  }
+  const [ret, refCount] = ZipStreamCache[path];
+  ZipStreamCache[path] = [ret, refCount + 1];
+  console.log(`acquire ${path} ${refCount + 1}`);
+  return ret;
+}
+
+function releaseZip(path: string) {
+  const obj = ZipStreamCache[path];
+  if (obj === undefined) throw new Error("error! key invalid");
+  const [ref, refCount] = obj;
+  console.log(`release ${path} : ${refCount}`);
+  if (refCount === 1) {
+    ref.close();
+    delete ZipStreamCache[path];
+    return;
+  }
+  ZipStreamCache[path] = [ref, refCount - 1];
+}
+
+async function renderZipImage(ctx: Context, path: string, page: number) {
+  const image_ext = ["gif", "png", "jpeg", "bmp", "webp", "jpg"];
+  console.log(`opened ${page}`);
+  let zip = await acquireZip(path);
+  const entries = entriesByNaturalOrder(zip).filter((x) => {
+    const ext = x.name.split(".").pop();
+    return ext !== undefined && image_ext.includes(ext);
+  });
+  if (0 <= page && page < entries.length) {
+    const entry = entries[page];
+    const last_modified = new Date(entry.time);
+    if (since_last_modified(ctx, last_modified)) {
+      return;
+    }
+    const read_stream = (await createReadableStreamFromZip(zip, entry));
+    /**Exceptions (ECONNRESET, ECONNABORTED) may be thrown when processing this request 
+     * for reasons such as when the browser unexpectedly closes the connection. 
+     * Once such an exception is raised, the stream is not properly destroyed, 
+     * so there is a problem with the zlib stream being accessed even after the stream is closed.
+     * So it waits for 100 ms and releases it.
+     * Additionaly, there is a risk of memory leak becuase zlib stream is not properly destroyed.
+     * @todo modify function 'stream' in 'node-stream-zip' library to prevent memory leak*/
+    read_stream.once("close", () => {
+      setTimeout(() => {
+        releaseZip(path);
+      }, 100);
     });
-    if(0 <= page && page < entries.length){
-        const entry = entries[page];
-        const last_modified = new Date(entry.time);
-        if(since_last_modified(ctx,last_modified)){
-            return;
-        }
-        const read_stream = (await createReadStreamFromZip(zip,entry));
-        read_stream.on('close',()=>zip.close());
-        ctx.body = read_stream;
-        ctx.response.length = entry.size;
-        //console.log(`${entry.name}'s ${page}:${entry.size}`);
-        ctx.response.type = entry.name.split(".").pop() as string;
-        ctx.status = 200;
-        ctx.set('Date', new Date().toUTCString());
-        ctx.set("Last-Modified",last_modified.toUTCString());
-    }
-    else{
-        ctx.status = 404;
-    }
+
+    ctx.body = read_stream;
+    ctx.response.length = entry.size;
+    //console.log(`${entry.name}'s ${page}:${entry.size}`);
+    ctx.response.type = entry.name.split(".").pop() as string;
+    ctx.status = 200;
+    ctx.set("Date", new Date().toUTCString());
+    ctx.set("Last-Modified", last_modified.toUTCString());
+  } else {
+    ctx.status = 404;
+  }
 }
 
-export class MangaRouter extends Router<ContentContext>{
-    constructor(){
-        super();
-        this.get("/",async (ctx,next)=>{
-            await renderZipImage(ctx,ctx.state.location.path,0);
-        });
-        this.get("/:page(\\d+)",async (ctx,next)=>{
-            const page = Number.parseInt(ctx.params['page']);
-            await renderZipImage(ctx,ctx.state.location.path,page);
-        });
-        this.get("/thumbnail", async (ctx,next)=>{
-            await renderZipImage(ctx,ctx.state.location.path,0);
-        });
-    }
+export class MangaRouter extends Router<ContentContext> {
+  constructor() {
+    super();
+    this.get("/", async (ctx, next) => {
+      await renderZipImage(ctx, ctx.state.location.path, 0);
+    });
+    this.get("/:page(\\d+)", async (ctx, next) => {
+      const page = Number.parseInt(ctx.params["page"]);
+      await renderZipImage(ctx, ctx.state.location.path, page);
+    });
+    this.get("/thumbnail", async (ctx, next) => {
+      await renderZipImage(ctx, ctx.state.location.path, 0);
+    });
+  }
 }
 
-export default MangaRouter;
\ No newline at end of file
+export default MangaRouter;
diff --git a/src/util/zipwrap.ts b/src/util/zipwrap.ts
index ee7e3bc..04db8ea 100644
--- a/src/util/zipwrap.ts
+++ b/src/util/zipwrap.ts
@@ -1,5 +1,6 @@
 import StreamZip, { ZipEntry } from 'node-stream-zip';
 import {orderBy} from 'natural-orderby';
+import { ReadStream } from 'fs';
 
 export async function readZip(path : string):Promise<StreamZip>{
     return new Promise((resolve,reject)=>{
@@ -22,7 +23,7 @@ export function entriesByNaturalOrder(zip: StreamZip){
     const ret = orderBy(Object.values(entries),v=>v.name);
     return ret;
 }
-export async function createReadStreamFromZip(zip:StreamZip,entry: ZipEntry):Promise<NodeJS.ReadableStream>{
+export async function createReadableStreamFromZip(zip:StreamZip,entry: ZipEntry):Promise<NodeJS.ReadableStream>{
     return new Promise((resolve,reject)=>{
         zip.stream(entry,(err, stream)=>{
             if(stream !== undefined){
@@ -35,7 +36,7 @@ export async function createReadStreamFromZip(zip:StreamZip,entry: ZipEntry):Pro
     );
 }
 export async function readAllFromZip(zip:StreamZip,entry: ZipEntry):Promise<Buffer>{
-    const stream = await createReadStreamFromZip(zip,entry);
+    const stream = await createReadableStreamFromZip(zip,entry);
     const chunks:Uint8Array[] = [];
     return new Promise((resolve,reject)=>{
         stream.on('data',(data)=>{chunks.push(data)});