diff --git a/rpxy-lib/src/error.rs b/rpxy-lib/src/error.rs
index 2763d1e..343cf04 100644
--- a/rpxy-lib/src/error.rs
+++ b/rpxy-lib/src/error.rs
@@ -97,6 +97,18 @@ pub enum RpxyError {
   #[error("Failed to acquire mutex lock for cache")]
   FailedToAcquiredMutexLockForCache,
 
+  #[cfg(feature = "cache")]
+  #[error("Failed to create file cache")]
+  FailedToCreateFileCache,
+
+  #[cfg(feature = "cache")]
+  #[error("Failed to write file cache")]
+  FailedToWriteFileCache,
+
+  #[cfg(feature = "cache")]
+  #[error("Failed to open cache file")]
+  FailedToOpenCacheFile,
+
   // Upstream connection setting errors
   #[error("Unsupported upstream option")]
   UnsupportedUpstreamOption,
diff --git a/rpxy-lib/src/forwarder/cache.rs b/rpxy-lib/src/forwarder/cache.rs
index ea29a41..03755e6 100644
--- a/rpxy-lib/src/forwarder/cache.rs
+++ b/rpxy-lib/src/forwarder/cache.rs
@@ -1,15 +1,22 @@
 use crate::{error::*, globals::Globals, log::*};
+use bytes::{Buf, Bytes, BytesMut};
 use http::{Request, Response};
+use http_body_util::StreamBody;
 use http_cache_semantics::CachePolicy;
 use lru::LruCache;
 use std::{
+  convert::Infallible,
   path::{Path, PathBuf},
   sync::{
     atomic::{AtomicUsize, Ordering},
     Arc, Mutex,
   },
 };
-use tokio::{fs, sync::RwLock};
+use tokio::{
+  fs::{self, File},
+  io::{AsyncReadExt, AsyncWriteExt},
+  sync::RwLock,
+};
 
 /* ---------------------------------------------- */
 #[derive(Clone, Debug)]
@@ -54,6 +61,14 @@ impl RpxyCache {
       max_each_size_on_memory,
     })
   }
+
+  /// Count cache entries
+  pub async fn count(&self) -> (usize, usize, usize) {
+    let total = self.inner.count();
+    let file = self.file_store.count().await;
+    let on_memory = total - file;
+    (total, on_memory, file)
+  }
 }
 
 /* ---------------------------------------------- */
@@ -71,6 +86,32 @@ impl FileStore {
   }
 }
 
+impl FileStore {
+  /// Count file cache entries
+  async fn count(&self) -> usize {
+    let inner = self.inner.read().await;
+    inner.cnt
+  }
+  /// Create a temporary file cache
+  async fn create(&mut self, cache_filename: &str, body_bytes: &Bytes) -> RpxyResult<CacheFileOrOnMemory> {
+    let mut inner = self.inner.write().await;
+    inner.create(cache_filename, body_bytes).await
+  }
+  // /// Evict a temporary file cache
+  // async fn evict(&self, path: impl AsRef<Path>) {
+  //   // Acquire the write lock
+  //   let mut inner = self.inner.write().await;
+  //   if let Err(e) = inner.remove(path).await {
+  //     warn!("Eviction failed during file object removal: {:?}", e);
+  //   };
+  // }
+  // /// Read a temporary file cache
+  // async fn read(&self, path: impl AsRef<Path>) -> RpxyResult<Bytes> {
+  //   let inner = self.inner.read().await;
+  //   inner.read(&path).await
+  // }
+}
+
 #[derive(Debug)]
 /// Manager inner for cache on file system
 struct FileStoreInner {
@@ -98,6 +139,67 @@ impl FileStoreInner {
       runtime_handle: runtime_handle.clone(),
     }
   }
+
+  /// Create a new temporary file cache
+  async fn create(&mut self, cache_filename: &str, body_bytes: &Bytes) -> RpxyResult<CacheFileOrOnMemory> {
+    let cache_filepath = self.cache_dir.join(cache_filename);
+    let Ok(mut file) = File::create(&cache_filepath).await else {
+      return Err(RpxyError::FailedToCreateFileCache);
+    };
+    let mut bytes_clone = body_bytes.clone();
+    while bytes_clone.has_remaining() {
+      if let Err(e) = file.write_buf(&mut bytes_clone).await {
+        error!("Failed to write file cache: {e}");
+        return Err(RpxyError::FailedToWriteFileCache);
+      };
+    }
+    self.cnt += 1;
+    Ok(CacheFileOrOnMemory::File(cache_filepath))
+  }
+
+  /// Retrieve a stored temporary file cache
+  async fn read(&self, path: impl AsRef<Path>) -> RpxyResult<()> {
+    let Ok(mut file) = File::open(&path).await else {
+      warn!("Cache file object cannot be opened");
+      return Err(RpxyError::FailedToOpenCacheFile);
+    };
+
+    /* ----------------------------- */
+    // PoC for streaming body
+    use futures::channel::mpsc;
+    let (tx, rx) = mpsc::unbounded::<Result<hyper::body::Frame<bytes::Bytes>, Infallible>>();
+
+    // let (body_sender, res_body) = Body::channel();
+    self.runtime_handle.spawn(async move {
+      //   let mut sender = body_sender;
+      let mut buf = BytesMut::new();
+      loop {
+        match file.read_buf(&mut buf).await {
+          Ok(0) => break,
+          Ok(_) => tx
+            .unbounded_send(Ok(hyper::body::Frame::data(buf.copy_to_bytes(buf.remaining()))))
+            .map_err(|e| anyhow::anyhow!("Failed to read cache file: {e}"))?,
+          //sender.send_data(buf.copy_to_bytes(buf.remaining())).await?,
+          Err(_) => break,
+        };
+      }
+      Ok(()) as anyhow::Result<()>
+    });
+
+    let mut rx = http_body_util::StreamBody::new(rx);
+    // TODO: 結局incominglikeなbodystreamを定義することになる。これだったらh3と合わせて自分で定義した方が良さそう。
+    // typeが長すぎるのでwrapperを作った方がいい。
+    // let response = Response::builder()
+    //   .status(200)
+    //   .header("content-type", "application/octet-stream")
+    //   .body(rx)
+    //   .unwrap();
+
+    todo!()
+    /* ----------------------------- */
+
+    // Ok(res_body)
+  }
 }
 
 /* ---------------------------------------------- */
diff --git a/rpxy-lib/src/forwarder/client.rs b/rpxy-lib/src/forwarder/client.rs
index 5718f2e..c6c6218 100644
--- a/rpxy-lib/src/forwarder/client.rs
+++ b/rpxy-lib/src/forwarder/client.rs
@@ -75,9 +75,12 @@ where
       };
       let (parts, body) = res.unwrap().into_parts();
 
+      // TODO: This is inefficient since current strategy needs to copy the whole body onto memory to cache it.
+      // This should be handled by copying buffer simultaneously while forwarding response to downstream.
       let Ok(bytes) = body.collect().await.map(|v| v.to_bytes()) else {
         return Err(RpxyError::FailedToWriteByteBufferForCache);
       };
+      let bytes_clone = bytes.clone();
 
       // TODO: this is inefficient. needs to be reconsidered to avoid unnecessary copy and should spawn async task to store cache.
       // We may need to use the same logic as h3.
diff --git a/rpxy-lib/src/proxy/proxy_h3.rs b/rpxy-lib/src/proxy/proxy_h3.rs
index d194b1f..1846d67 100644
--- a/rpxy-lib/src/proxy/proxy_h3.rs
+++ b/rpxy-lib/src/proxy/proxy_h3.rs
@@ -153,20 +153,40 @@ where
       )
       .await?;
 
-    let (new_res_parts, new_body) = res.into_parts();
+    let (new_res_parts, mut new_body) = res.into_parts();
     let new_res = Response::from_parts(new_res_parts, ());
 
     match send_stream.send_response(new_res).await {
       Ok(_) => {
         debug!("HTTP/3 response to connection successful");
-        // aggregate body without copying
-        let body_data = new_body
-          .collect()
-          .await
+        loop {
+          let frame = match new_body.frame().await {
+            Some(frame) => frame,
+            None => {
+              debug!("Response body finished");
+              break;
+            }
+          }
           .map_err(|e| RpxyError::HyperBodyManipulationError(e.to_string()))?;
 
-        // create stream body to save memory, shallow copy (increment of ref-count) to Bytes using copy_to_bytes inside to_bytes()
-        send_stream.send_data(body_data.to_bytes()).await?;
+          if frame.is_data() {
+            let data = frame.into_data().unwrap_or_default();
+            debug!("Write data to HTTP/3 stream");
+            send_stream.send_data(data).await?;
+          } else if frame.is_trailers() {
+            let trailers = frame.into_trailers().unwrap_or_default();
+            debug!("Write trailer to HTTP/3 stream");
+            send_stream.send_trailers(trailers).await?;
+          }
+        }
+        // // aggregate body without copying
+        // let body_data = new_body
+        //   .collect()
+        //   .await
+        //   .map_err(|e| RpxyError::HyperBodyManipulationError(e.to_string()))?;
+
+        // // create stream body to save memory, shallow copy (increment of ref-count) to Bytes using copy_to_bytes inside to_bytes()
+        // send_stream.send_data(body_data.to_bytes()).await?;
 
         // TODO: needs handling trailer? should be included in body from handler.
       }