diff --git a/Cargo.lock b/Cargo.lock
index e53cbf9..607571c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2896,7 +2896,7 @@ dependencies = [
 
 [[package]]
 name = "uzumibi-cli"
-version = "0.7.1"
+version = "0.8.0"
 dependencies = [
  "clap",
  "dialoguer",
@@ -2905,18 +2905,7 @@ dependencies = [
 
 [[package]]
 name = "uzumibi-cloudflare-ext"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8ee0e8e2a653d9586d7c0e66379017f544e6db895a2deee0ec2a88e6ce6ca6ae"
-dependencies = [
- "mrubyedge",
- "mrubyedge-serde-json",
- "uzumibi-gem 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
-name = "uzumibi-cloudflare-ext"
-version = "0.2.2"
+version = "0.3.1"
 dependencies = [
  "mrubyedge",
  "mrubyedge-serde-json",
@@ -2983,7 +2972,7 @@ dependencies = [
  "mrubyedge",
  "mrubyedge-serde-json",
  "uzumibi-art-router 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "uzumibi-cloudflare-ext 0.2.1",
+ "uzumibi-cloudflare-ext",
  "uzumibi-gem 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
diff --git a/uzumibi-cli/Cargo.toml b/uzumibi-cli/Cargo.toml
index 5260e26..07a4f8c 100644
--- a/uzumibi-cli/Cargo.toml
+++ b/uzumibi-cli/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "uzumibi-cli"
-version = "0.7.1"
+version = "0.8.0"
 edition = "2024"
 authors = ["Uchio Kondo <udzura@udzura.jp>"]
 description = "Uzumibi CLI tool to generate serverless mruby/edge apps"
diff --git a/uzumibi-cli/src/main.rs b/uzumibi-cli/src/main.rs
index fd90967..ba68b09 100644
--- a/uzumibi-cli/src/main.rs
+++ b/uzumibi-cli/src/main.rs
@@ -374,10 +374,25 @@ fn print_project_next_steps(template: &str, _project_name: &str, features: &[Str
             println!();
             println!("  1. Install dependencies:");
             println!("     \x1b[36mpnpm install\x1b[0m");
-            println!("  2. Build and start development server:");
-            println!("     \x1b[36mpnpm run dev\x1b[0m");
-            println!("  3. Deploy to Cloudflare:");
-            println!("     \x1b[36mpnpm run deploy\x1b[0m");
+            if has_enable_external || has_queue {
+                println!("  2. Set up a KV namespace for Uzumibi::KV:");
+                println!("     • Create a new namespace:");
+                println!("     \x1b[36mnpx wrangler kv namespace create UZUMIBI_KV\x1b[0m");
+                println!("     • Or list existing namespaces to reuse one:");
+                println!("     \x1b[36mnpx wrangler kv namespace list\x1b[0m");
+                println!(
+                    "     Then replace \x1b[36m<YOUR_KV_NAMESPACE_ID>\x1b[0m in \x1b[36mwrangler.jsonc\x1b[0m with the namespace ID."
+                );
+                println!("  3. Build and start development server:");
+                println!("     \x1b[36mpnpm run dev\x1b[0m");
+                println!("  4. Deploy to Cloudflare:");
+                println!("     \x1b[36mpnpm run deploy\x1b[0m");
+            } else {
+                println!("  2. Build and start development server:");
+                println!("     \x1b[36mpnpm run dev\x1b[0m");
+                println!("  3. Deploy to Cloudflare:");
+                println!("     \x1b[36mpnpm run deploy\x1b[0m");
+            }
             if has_queue {
                 println!();
                 println!(
@@ -394,7 +409,10 @@ fn print_project_next_steps(template: &str, _project_name: &str, features: &[Str
                     "    • \x1b[36mUzumibi::Fetch.fetch(url, method, body)\x1b[0m → Uzumibi::Response"
                 );
                 println!(
-                    "    • \x1b[36mUzumibi::KV.get(key)\x1b[0m / \x1b[36mUzumibi::KV.set(key, value)\x1b[0m → Durable Object storage"
+                    "    • \x1b[36mUzumibi::KV.get(key)\x1b[0m / \x1b[36mUzumibi::KV.set(key, value)\x1b[0m → Cloudflare KV"
+                );
+                println!(
+                    "    • \x1b[36mUzumibi::LegacyKV.get(key)\x1b[0m / \x1b[36mUzumibi::LegacyKV.set(key, value)\x1b[0m → Durable Object storage"
                 );
                 println!(
                     "    • \x1b[36mUzumibi::Queue.send(queue_name, message)\x1b[0m → Cloudflare Queue"
@@ -407,7 +425,10 @@ fn print_project_next_steps(template: &str, _project_name: &str, features: &[Str
                     "    • \x1b[36mUzumibi::Fetch.fetch(url, method, body)\x1b[0m → Uzumibi::Response"
                 );
                 println!(
-                    "    • \x1b[36mUzumibi::KV.get(key)\x1b[0m / \x1b[36mUzumibi::KV.set(key, value)\x1b[0m → Durable Object storage"
+                    "    • \x1b[36mUzumibi::KV.get(key)\x1b[0m / \x1b[36mUzumibi::KV.set(key, value)\x1b[0m → Cloudflare KV"
+                );
+                println!(
+                    "    • \x1b[36mUzumibi::LegacyKV.get(key)\x1b[0m / \x1b[36mUzumibi::LegacyKV.set(key, value)\x1b[0m → Durable Object storage"
                 );
                 println!(
                     "    • \x1b[36mUzumibi::Queue.send(queue_name, message)\x1b[0m → Cloudflare Queue"
diff --git a/uzumibi-cli/templates/cloudflare/__features__/enable-external/src/index.js b/uzumibi-cli/templates/cloudflare/__features__/enable-external/src/index.js
index 6c91ff7..537c981 100644
--- a/uzumibi-cli/templates/cloudflare/__features__/enable-external/src/index.js
+++ b/uzumibi-cli/templates/cloudflare/__features__/enable-external/src/index.js
@@ -5,7 +5,7 @@ import mod from "./$$PROJECT_NAME_UNDERSCORE$$.wasm";
 const wasmModule = mod;
 
 /**
- * Durable Object for Uzumibi::KV storage
+ * Durable Object storage retained for Uzumibi::LegacyKV.
  */
 export class UzumibiKVObject extends DurableObject {
     async get(key) {
@@ -27,7 +27,9 @@ export default {
 
         const query = new URL(request.url).searchParams;
 
-        // Durable Object stub (if binding exists)
+        const kv = env.UZUMIBI_KV ?? null;
+
+        // Durable Object stub retained for Uzumibi::LegacyKV.
         const doStub = env.UZUMIBI_KV_DATA
             ? env.UZUMIBI_KV_DATA.getByName("default")
             : null;
@@ -137,7 +139,35 @@ export default {
                     return pos;
                 },
 
-                // KV.get(key) -> value string (via Durable Object)
+                // KV.get(key) -> value string
+                uzumibi_cf_kv_get: async (keyPtr, keySize, resultPtr, resultMaxSize) => {
+                    if (!kv) return -1;
+                    const memory = exports.memory;
+                    const key = decoder.decode(new Uint8Array(memory.buffer, keyPtr, keySize));
+
+                    const value = await kv.get(key);
+                    if (value === null) {
+                        return -1;
+                    }
+                    const valueBytes = encoder.encode(value);
+                    const length = Math.min(valueBytes.length, resultMaxSize);
+                    const resultBuffer = new Uint8Array(memory.buffer, resultPtr, resultMaxSize);
+                    resultBuffer.set(valueBytes.slice(0, length));
+                    return length;
+                },
+
+                // KV.set(key, value)
+                uzumibi_cf_kv_set: async (keyPtr, keySize, valuePtr, valueSize) => {
+                    if (!kv) return -1;
+                    const memory = exports.memory;
+                    const key = decoder.decode(new Uint8Array(memory.buffer, keyPtr, keySize));
+                    const value = decoder.decode(new Uint8Array(memory.buffer, valuePtr, valueSize));
+
+                    await kv.put(key, value);
+                    return 0;
+                },
+
+                // LegacyKV.get(key) -> value string (via Durable Object)
                 uzumibi_cf_durable_object_get: async (keyPtr, keySize, resultPtr, resultMaxSize) => {
                     if (!doStub) return -1;
                     const memory = exports.memory;
@@ -154,7 +184,7 @@ export default {
                     return length;
                 },
 
-                // KV.set(key, value) (via Durable Object)
+                // LegacyKV.set(key, value) (via Durable Object)
                 uzumibi_cf_durable_object_set: async (keyPtr, keySize, valuePtr, valueSize) => {
                     if (!doStub) return -1;
                     const memory = exports.memory;
diff --git a/uzumibi-cli/templates/cloudflare/__features__/enable-external/wasm-app/Cargo.toml_ b/uzumibi-cli/templates/cloudflare/__features__/enable-external/wasm-app/Cargo.toml_
index 9509fb9..cc0a682 100644
--- a/uzumibi-cli/templates/cloudflare/__features__/enable-external/wasm-app/Cargo.toml_
+++ b/uzumibi-cli/templates/cloudflare/__features__/enable-external/wasm-app/Cargo.toml_
@@ -12,7 +12,7 @@ mrubyedge = { version = ">= 1.1.12", features = [
 ], default-features = false }
 uzumibi-gem = ">= 0.6.0"
 uzumibi-art-router = ">= 0.3.1"
-uzumibi-cloudflare-ext = ">= 0.2.2"
+uzumibi-cloudflare-ext = ">= 0.3.1"
 mrubyedge-serde-json = ">= 0.1.2"
 
 [build-dependencies]
diff --git a/uzumibi-cli/templates/cloudflare/__features__/enable-external/wrangler.jsonc b/uzumibi-cli/templates/cloudflare/__features__/enable-external/wrangler.jsonc
index 08e3213..aec6c66 100644
--- a/uzumibi-cli/templates/cloudflare/__features__/enable-external/wrangler.jsonc
+++ b/uzumibi-cli/templates/cloudflare/__features__/enable-external/wrangler.jsonc
@@ -19,6 +19,17 @@
         "directory": "./public",
         "binding": "ASSETS"
     },
+    /**
+	 * KV Namespace
+	 * Used for Uzumibi::KV.get/set.
+	 * Replace the placeholder with a namespace ID from `wrangler kv namespace create`.
+	 */
+    "kv_namespaces": [
+        {
+            "binding": "UZUMIBI_KV",
+            "id": "<YOUR_KV_NAMESPACE_ID>"
+        }
+    ],
     /**
 	 * Queues
 	 * Used for Uzumibi::Queue.send
@@ -36,7 +47,7 @@
     // },
     /**
 	 * Durable Objects
-	 * Used for Uzumibi::KV.get/set
+     * Used for Uzumibi::LegacyKV.get/set
 	 * https://developers.cloudflare.com/durable-objects/
 	 */
     "durable_objects": {
diff --git a/uzumibi-cli/templates/cloudflare/__features__/queue/src/index.js b/uzumibi-cli/templates/cloudflare/__features__/queue/src/index.js
index eb41615..c5c7f4d 100644
--- a/uzumibi-cli/templates/cloudflare/__features__/queue/src/index.js
+++ b/uzumibi-cli/templates/cloudflare/__features__/queue/src/index.js
@@ -5,7 +5,7 @@ import mod from "./$$PROJECT_NAME_UNDERSCORE$$_queue.wasm";
 const wasmModule = mod;
 
 /**
- * Durable Object for Uzumibi::KV storage
+ * Durable Object storage retained for Uzumibi::LegacyKV.
  */
 export class UzumibiKVObject extends DurableObject {
     async get(key) {
@@ -27,7 +27,9 @@ export default {
         const decoder = new TextDecoder();
         const encoder = new TextEncoder();
 
-        // Durable Object stub (if binding exists)
+        const kv = env.UZUMIBI_KV ?? null;
+
+        // Durable Object stub retained for Uzumibi::LegacyKV.
         const doStub = env.UZUMIBI_KV_DATA
             ? env.UZUMIBI_KV_DATA.getByName("default")
             : null;
@@ -133,7 +135,34 @@ export default {
                     return pos;
                 },
 
-                // KV.get(key) -> value string (via Durable Object)
+                // KV.get(key) -> value string
+                uzumibi_cf_kv_get: async (keyPtr, keySize, resultPtr, resultMaxSize) => {
+                    if (!kv) return -1;
+                    const memory = exports.memory;
+                    const key = decoder.decode(new Uint8Array(memory.buffer, keyPtr, keySize));
+
+                    const value = await kv.get(key);
+                    if (value === null) return -1;
+
+                    const valueBytes = encoder.encode(value);
+                    const length = Math.min(valueBytes.length, resultMaxSize);
+                    const resultBuffer = new Uint8Array(memory.buffer, resultPtr, resultMaxSize);
+                    resultBuffer.set(valueBytes.slice(0, length));
+                    return length;
+                },
+
+                // KV.set(key, value)
+                uzumibi_cf_kv_set: async (keyPtr, keySize, valuePtr, valueSize) => {
+                    if (!kv) return -1;
+                    const memory = exports.memory;
+                    const key = decoder.decode(new Uint8Array(memory.buffer, keyPtr, keySize));
+                    const value = decoder.decode(new Uint8Array(memory.buffer, valuePtr, valueSize));
+
+                    await kv.put(key, value);
+                    return 0;
+                },
+
+                // LegacyKV.get(key) -> value string (via Durable Object)
                 uzumibi_cf_durable_object_get: async (keyPtr, keySize, resultPtr, resultMaxSize) => {
                     if (!doStub) return -1;
                     const memory = exports.memory;
@@ -149,7 +178,7 @@ export default {
                     return length;
                 },
 
-                // KV.set(key, value) (via Durable Object)
+                // LegacyKV.set(key, value) (via Durable Object)
                 uzumibi_cf_durable_object_set: async (keyPtr, keySize, valuePtr, valueSize) => {
                     if (!doStub) return -1;
                     const memory = exports.memory;
diff --git a/uzumibi-cli/templates/cloudflare/__features__/queue/wasm-app/Cargo.toml_ b/uzumibi-cli/templates/cloudflare/__features__/queue/wasm-app/Cargo.toml_
index c5fea81..e8e617d 100644
--- a/uzumibi-cli/templates/cloudflare/__features__/queue/wasm-app/Cargo.toml_
+++ b/uzumibi-cli/templates/cloudflare/__features__/queue/wasm-app/Cargo.toml_
@@ -12,7 +12,7 @@ mrubyedge = { version = ">= 1.1.12", features = [
 ], default-features = false }
 uzumibi-gem = ">= 0.6.0"
 uzumibi-art-router = ">= 0.3.1"
-uzumibi-cloudflare-ext = ">= 0.2.0"
+uzumibi-cloudflare-ext = ">= 0.3.1"
 mrubyedge-serde-json = ">= 0.1.2"
 
 [build-dependencies]
diff --git a/uzumibi-cli/templates/cloudflare/__features__/queue/wrangler.jsonc b/uzumibi-cli/templates/cloudflare/__features__/queue/wrangler.jsonc
index 7f1510f..381de9c 100644
--- a/uzumibi-cli/templates/cloudflare/__features__/queue/wrangler.jsonc
+++ b/uzumibi-cli/templates/cloudflare/__features__/queue/wrangler.jsonc
@@ -11,9 +11,20 @@
     "observability": {
         "enabled": true
     },
+    /**
+	 * KV Namespace
+	 * Used for Uzumibi::KV.get/set.
+	 * Replace the placeholder with a namespace ID from `wrangler kv namespace create`.
+	 */
+    "kv_namespaces": [
+        {
+            "binding": "UZUMIBI_KV",
+            "id": "<YOUR_KV_NAMESPACE_ID>"
+        }
+    ],
     /**
 	 * Durable Objects
-	 * Used for Uzumibi::KV.get/set
+     * Used for Uzumibi::LegacyKV.get/set
 	 * https://developers.cloudflare.com/durable-objects/
 	 */
     "durable_objects": {
diff --git a/uzumibi-cli/templates/cloudflare/wasm-app/Cargo.toml_ b/uzumibi-cli/templates/cloudflare/wasm-app/Cargo.toml_
index a3e9df6..d6b2e7c 100644
--- a/uzumibi-cli/templates/cloudflare/wasm-app/Cargo.toml_
+++ b/uzumibi-cli/templates/cloudflare/wasm-app/Cargo.toml_
@@ -12,7 +12,7 @@ mrubyedge = { version = ">= 1.1.12", features = [
 ], default-features = false }
 uzumibi-gem = ">= 0.6.0"
 uzumibi-art-router = ">= 0.3.1"
-uzumibi-cloudflare-ext = ">= 0.2.0"
+uzumibi-cloudflare-ext = ">= 0.3.1"
 mrubyedge-serde-json = ">= 0.1.2"
 
 [build-dependencies]
diff --git a/uzumibi-cli/tests/runn/new_cloudflare.yml b/uzumibi-cli/tests/runn/new_cloudflare.yml
index bc3f64a..faa354b 100644
--- a/uzumibi-cli/tests/runn/new_cloudflare.yml
+++ b/uzumibi-cli/tests/runn/new_cloudflare.yml
@@ -70,6 +70,7 @@ steps:
     desc: Build the WASM app
     exec:
       command: cd {{ vars.tmpdir }}/{{ vars.project_name }}/wasm-app && cargo build --target wasm32-unknown-unknown --release
+    dump: steps
     test: current.exit_code == 0
 
   start_server:
diff --git a/uzumibi-cloudflare-ext/Cargo.toml b/uzumibi-cloudflare-ext/Cargo.toml
index b96bda9..2b06540 100644
--- a/uzumibi-cloudflare-ext/Cargo.toml
+++ b/uzumibi-cloudflare-ext/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "uzumibi-cloudflare-ext"
-version = "0.2.2"
+version = "0.3.1"
 edition = "2024"
 authors = ["Uchio Kondo <udzura@udzura.jp>"]
 description = "Cloudflare Workers extension for Uzumibi (mruby/edge serverless framework)"
diff --git a/uzumibi-cloudflare-ext/src/lib.rs b/uzumibi-cloudflare-ext/src/lib.rs
index 13624dd..7ea8bb1 100644
--- a/uzumibi-cloudflare-ext/src/lib.rs
+++ b/uzumibi-cloudflare-ext/src/lib.rs
@@ -19,11 +19,14 @@ pub const PASS_ASSETS: u64 = 0xFEFFFFFF;
 
 // ---- Cloudflare-specific extern C declarations ----
 
+// Host functions are supplied by the Worker's JavaScript importObject under the "env" module.
+#[link(wasm_import_module = "env")]
 unsafe extern "C" {
     unsafe fn debug_console_log(ptr: *const u8, len: usize);
 }
 
 #[cfg(feature = "queue")]
+#[link(wasm_import_module = "env")]
 unsafe extern "C" {
     unsafe fn uzumibi_cf_message_ack(message_id_ptr: *const u8, message_id_size: usize) -> i32;
     unsafe fn uzumibi_cf_message_retry(
@@ -34,6 +37,7 @@ unsafe extern "C" {
 }
 
 #[cfg(feature = "enable-external")]
+#[link(wasm_import_module = "env")]
 unsafe extern "C" {
     unsafe fn uzumibi_cf_fetch(
         url_ptr: *const u8,
@@ -47,6 +51,18 @@ unsafe extern "C" {
         result_ptr: *mut u8,
         result_max_size: usize,
     ) -> i32;
+    unsafe fn uzumibi_cf_kv_get(
+        key_ptr: *const u8,
+        key_size: usize,
+        result_ptr: *mut u8,
+        result_max_size: usize,
+    ) -> i32;
+    unsafe fn uzumibi_cf_kv_set(
+        key_ptr: *const u8,
+        key_size: usize,
+        value_ptr: *const u8,
+        value_size: usize,
+    ) -> i32;
     unsafe fn uzumibi_cf_durable_object_get(
         key_ptr: *const u8,
         key_size: usize,
@@ -117,6 +133,37 @@ fn cf_fetch(url: &str, method: &str, body: &str, headers: &[u8]) -> Result<Vec<u
     }
 }
 
+#[cfg(feature = "enable-external")]
+fn cf_kv_get(key: &str) -> Result<Option<String>, String> {
+    const BUFFER_SIZE: usize = 65536;
+    let mut buffer = vec![0u8; BUFFER_SIZE];
+
+    unsafe {
+        let result = uzumibi_cf_kv_get(key.as_ptr(), key.len(), buffer.as_mut_ptr(), BUFFER_SIZE);
+        match result {
+            -1 => Ok(None),
+            len if len >= 0 => {
+                let len = len as usize;
+                let value = String::from_utf8(buffer[..len].to_vec())
+                    .map_err(|e| format!("Failed to decode UTF-8: {}", e))?;
+                Ok(Some(value))
+            }
+            _ => Err(format!("Unexpected return value from kv_get: {}", result)),
+        }
+    }
+}
+
+#[cfg(feature = "enable-external")]
+fn cf_kv_set(key: &str, value: &str) -> Result<(), String> {
+    unsafe {
+        let result = uzumibi_cf_kv_set(key.as_ptr(), key.len(), value.as_ptr(), value.len());
+        match result {
+            0 => Ok(()),
+            _ => Err(format!("Failed to set value: return code {}", result)),
+        }
+    }
+}
+
 #[cfg(feature = "enable-external")]
 fn cf_durable_object_get(key: &str) -> Result<Option<String>, String> {
     const BUFFER_SIZE: usize = 65536;
@@ -374,7 +421,7 @@ fn uzumibi_kv_class_get(
     let key = mrb_funcall(vm, key_obj.clone().into(), "to_s", &[])?;
     let key: String = key.as_ref().try_into()?;
 
-    match cf_durable_object_get(&key) {
+    match cf_kv_get(&key) {
         Ok(Some(value)) => Ok(RObject::string(value).to_refcount_assigned()),
         Ok(None) => Ok(RObject::nil().to_refcount_assigned()),
         Err(e) => Err(mrubyedge::Error::RuntimeError(format!(
@@ -398,13 +445,54 @@ fn uzumibi_kv_class_set(
     let value = mrb_funcall(vm, value_obj.clone().into(), "to_s", &[])?;
     let value: String = value.as_ref().try_into()?;
 
-    cf_durable_object_set(&key, &value).map_err(|e| {
+    cf_kv_set(&key, &value).map_err(|e| {
         mrubyedge::Error::RuntimeError(format!("Failed to set storage value: {}", e))
     })?;
 
     Ok(RObject::boolean(true).to_refcount_assigned())
 }
 
+/// LegacyKV.get(key)
+#[cfg(feature = "enable-external")]
+fn uzumibi_legacy_kv_class_get(
+    vm: &mut VM,
+    args: &[Rc<RObject>],
+) -> Result<Rc<RObject>, mrubyedge::Error> {
+    let key_obj = &args[0];
+    let key = mrb_funcall(vm, key_obj.clone().into(), "to_s", &[])?;
+    let key: String = key.as_ref().try_into()?;
+
+    match cf_durable_object_get(&key) {
+        Ok(Some(value)) => Ok(RObject::string(value).to_refcount_assigned()),
+        Ok(None) => Ok(RObject::nil().to_refcount_assigned()),
+        Err(e) => Err(mrubyedge::Error::RuntimeError(format!(
+            "Failed to access legacy storage value: {}",
+            e
+        ))),
+    }
+}
+
+/// LegacyKV.set(key, value)
+#[cfg(feature = "enable-external")]
+fn uzumibi_legacy_kv_class_set(
+    vm: &mut VM,
+    args: &[Rc<RObject>],
+) -> Result<Rc<RObject>, mrubyedge::Error> {
+    let key_obj = &args[0];
+    let key = mrb_funcall(vm, key_obj.clone().into(), "to_s", &[])?;
+    let key: String = key.as_ref().try_into()?;
+
+    let value_obj = &args[1];
+    let value = mrb_funcall(vm, value_obj.clone().into(), "to_s", &[])?;
+    let value: String = value.as_ref().try_into()?;
+
+    cf_durable_object_set(&key, &value).map_err(|e| {
+        mrubyedge::Error::RuntimeError(format!("Failed to set legacy storage value: {}", e))
+    })?;
+
+    Ok(RObject::boolean(true).to_refcount_assigned())
+}
+
 /// Secret.get(key) -> String | nil
 #[cfg(feature = "enable-external")]
 fn uzumibi_secret_class_get(
@@ -728,6 +816,21 @@ pub fn init_cloudflare_ext(vm: &mut VM) {
         mrb_define_class_cmethod(vm, kv_class.clone(), "get", Box::new(uzumibi_kv_class_get));
         mrb_define_class_cmethod(vm, kv_class, "set", Box::new(uzumibi_kv_class_set));
 
+        // Uzumibi::LegacyKV.get(key) / Uzumibi::LegacyKV.set(key, value)
+        let legacy_kv_class = vm.define_class("LegacyKV", None, Some(uzumibi_module.clone()));
+        mrb_define_class_cmethod(
+            vm,
+            legacy_kv_class.clone(),
+            "get",
+            Box::new(uzumibi_legacy_kv_class_get),
+        );
+        mrb_define_class_cmethod(
+            vm,
+            legacy_kv_class,
+            "set",
+            Box::new(uzumibi_legacy_kv_class_set),
+        );
+
         // Uzumibi::Secret.get(key)
         let secret_class = vm.define_class("Secret", None, Some(uzumibi_module.clone()));
         mrb_define_class_cmethod(vm, secret_class, "get", Box::new(uzumibi_secret_class_get));
diff --git a/uzumibi-on-cloudflare-spike/.gitignore b/uzumibi-on-cloudflare-spike/.gitignore
index 9ee5478..652ddaf 100644
--- a/uzumibi-on-cloudflare-spike/.gitignore
+++ b/uzumibi-on-cloudflare-spike/.gitignore
@@ -1,4 +1,5 @@
+.wrangler
 node_modules/*
 wasm-app/target
 src/*.wasm
-*.mrb
\ No newline at end of file
+*.mrb
diff --git a/uzumibi-on-cloudflare-spike/lib/app.rb b/uzumibi-on-cloudflare-spike/lib/app.rb
index 4c9eaf5..6392cef 100644
--- a/uzumibi-on-cloudflare-spike/lib/app.rb
+++ b/uzumibi-on-cloudflare-spike/lib/app.rb
@@ -66,6 +66,20 @@ class App < Uzumibi::Router
     res
   end
 
+  get "/kv/:key" do |req, res|
+    value = Uzumibi::KV.get(req.params[:key])
+    if value
+      res.return(200, { "Content-Type" => "text/plain" }, value)
+    else
+      res.return(404, { "Content-Type" => "text/plain" }, "Key not found\n")
+    end
+  end
+
+  post "/kv/:key" do |req, res|
+    Uzumibi::KV.set(req.params[:key], req.body)
+    res.return(201, { "Content-Type" => "text/plain" }, "Stored\n")
+  end
+
   get "/assets/*" do |req, res|
     fetch_assets
   end
diff --git a/uzumibi-on-cloudflare-spike/src/index.js b/uzumibi-on-cloudflare-spike/src/index.js
index 35de2e7..388a946 100644
--- a/uzumibi-on-cloudflare-spike/src/index.js
+++ b/uzumibi-on-cloudflare-spike/src/index.js
@@ -5,7 +5,7 @@ import mod from "./uzumibi_on_cloudflare_spike.wasm";
 const wasmModule = mod;
 
 /**
- * Durable Object for Uzumibi::KV storage
+ * Durable Object storage retained for Uzumibi::LegacyKV.
  */
 export class UzumibiKVObject extends DurableObject {
 	async get(key) {
@@ -27,7 +27,9 @@ export default {
 
 		const query = new URL(request.url).searchParams;
 
-		// Durable Object stub (if binding exists)
+		const kv = env.UZUMIBI_KV ?? null;
+
+		// Durable Object stub retained for Uzumibi::LegacyKV.
 		const doStub = env.UZUMIBI_KV_DATA
 			? env.UZUMIBI_KV_DATA.getByName("default")
 			: null;
@@ -137,7 +139,35 @@ export default {
 					return pos;
 				},
 
-				// KV.get(key) -> value string (via Durable Object)
+				// KV.get(key) -> value string
+				uzumibi_cf_kv_get: async (keyPtr, keySize, resultPtr, resultMaxSize) => {
+					if (!kv) return -1;
+					const memory = exports.memory;
+					const key = decoder.decode(new Uint8Array(memory.buffer, keyPtr, keySize));
+
+					const value = await kv.get(key);
+					if (value === null) {
+						return -1;
+					}
+					const valueBytes = encoder.encode(value);
+					const length = Math.min(valueBytes.length, resultMaxSize);
+					const resultBuffer = new Uint8Array(memory.buffer, resultPtr, resultMaxSize);
+					resultBuffer.set(valueBytes.slice(0, length));
+					return length;
+				},
+
+				// KV.set(key, value)
+				uzumibi_cf_kv_set: async (keyPtr, keySize, valuePtr, valueSize) => {
+					if (!kv) return -1;
+					const memory = exports.memory;
+					const key = decoder.decode(new Uint8Array(memory.buffer, keyPtr, keySize));
+					const value = decoder.decode(new Uint8Array(memory.buffer, valuePtr, valueSize));
+
+					await kv.put(key, value);
+					return 0;
+				},
+
+				// LegacyKV.get(key) -> value string (via Durable Object)
 				uzumibi_cf_durable_object_get: async (keyPtr, keySize, resultPtr, resultMaxSize) => {
 					if (!doStub) return -1;
 					const memory = exports.memory;
@@ -154,7 +184,7 @@ export default {
 					return length;
 				},
 
-				// KV.set(key, value) (via Durable Object)
+				// LegacyKV.set(key, value) (via Durable Object)
 				uzumibi_cf_durable_object_set: async (keyPtr, keySize, valuePtr, valueSize) => {
 					if (!doStub) return -1;
 					const memory = exports.memory;
diff --git a/uzumibi-on-cloudflare-spike/src/index.queue.js b/uzumibi-on-cloudflare-spike/src/index.queue.js
index e18fa1f..55b0bfa 100644
--- a/uzumibi-on-cloudflare-spike/src/index.queue.js
+++ b/uzumibi-on-cloudflare-spike/src/index.queue.js
@@ -5,7 +5,7 @@ import mod from "./uzumibi_on_cloudflare_spike_queue.wasm";
 const wasmModule = mod;
 
 /**
- * Durable Object for Uzumibi::KV storage
+ * Durable Object storage retained for Uzumibi::LegacyKV.
  */
 export class UzumibiKVObject extends DurableObject {
 	async get(key) {
@@ -27,7 +27,9 @@ export default {
 		const decoder = new TextDecoder();
 		const encoder = new TextEncoder();
 
-		// Durable Object stub (if binding exists)
+		const kv = env.UZUMIBI_KV ?? null;
+
+		// Durable Object stub retained for Uzumibi::LegacyKV.
 		const doStub = env.UZUMIBI_KV_DATA
 			? env.UZUMIBI_KV_DATA.getByName("default")
 			: null;
@@ -133,7 +135,34 @@ export default {
 					return pos;
 				},
 
-				// KV.get(key) -> value string (via Durable Object)
+				// KV.get(key) -> value string
+				uzumibi_cf_kv_get: async (keyPtr, keySize, resultPtr, resultMaxSize) => {
+					if (!kv) return -1;
+					const memory = exports.memory;
+					const key = decoder.decode(new Uint8Array(memory.buffer, keyPtr, keySize));
+
+					const value = await kv.get(key);
+					if (value === null) return -1;
+
+					const valueBytes = encoder.encode(value);
+					const length = Math.min(valueBytes.length, resultMaxSize);
+					const resultBuffer = new Uint8Array(memory.buffer, resultPtr, resultMaxSize);
+					resultBuffer.set(valueBytes.slice(0, length));
+					return length;
+				},
+
+				// KV.set(key, value)
+				uzumibi_cf_kv_set: async (keyPtr, keySize, valuePtr, valueSize) => {
+					if (!kv) return -1;
+					const memory = exports.memory;
+					const key = decoder.decode(new Uint8Array(memory.buffer, keyPtr, keySize));
+					const value = decoder.decode(new Uint8Array(memory.buffer, valuePtr, valueSize));
+
+					await kv.put(key, value);
+					return 0;
+				},
+
+				// LegacyKV.get(key) -> value string (via Durable Object)
 				uzumibi_cf_durable_object_get: async (keyPtr, keySize, resultPtr, resultMaxSize) => {
 					if (!doStub) return -1;
 					const memory = exports.memory;
@@ -149,7 +178,7 @@ export default {
 					return length;
 				},
 
-				// KV.set(key, value) (via Durable Object)
+				// LegacyKV.set(key, value) (via Durable Object)
 				uzumibi_cf_durable_object_set: async (keyPtr, keySize, valuePtr, valueSize) => {
 					if (!doStub) return -1;
 					const memory = exports.memory;
diff --git a/uzumibi-on-cloudflare-spike/wasm-app/Cargo.toml b/uzumibi-on-cloudflare-spike/wasm-app/Cargo.toml
index 8a94341..edb90b1 100644
--- a/uzumibi-on-cloudflare-spike/wasm-app/Cargo.toml
+++ b/uzumibi-on-cloudflare-spike/wasm-app/Cargo.toml
@@ -13,7 +13,7 @@ mrubyedge = { version = ">= 1.1.10", features = [
 ], default-features = false }
 uzumibi-gem = ">= 0.6.0"
 uzumibi-art-router = ">= 0.3.1"
-uzumibi-cloudflare-ext = ">= 0.2.0"
+uzumibi-cloudflare-ext = { path = "../../uzumibi-cloudflare-ext" }
 mrubyedge-serde-json = ">= 0.1.2"
 
 [build-dependencies]
diff --git a/uzumibi-on-cloudflare-spike/wrangler.jsonc b/uzumibi-on-cloudflare-spike/wrangler.jsonc
index 1efd8e9..1f72b5b 100644
--- a/uzumibi-on-cloudflare-spike/wrangler.jsonc
+++ b/uzumibi-on-cloudflare-spike/wrangler.jsonc
@@ -30,9 +30,20 @@
 		"directory": "./public",
 		"binding": "ASSETS"
 	},
+	/**
+	 * KV Namespace
+	 * Used for Uzumibi::KV.get/set.
+	 * Replace the placeholder with a namespace ID from `wrangler kv namespace create`.
+	 */
+	"kv_namespaces": [
+		{
+			"binding": "UZUMIBI_KV",
+			"id": "e0bc3ab9504b4fc78a5b33b847ddbd19"
+		}
+	],
 	/**
 	 * Durable Objects
-	 * Used for Uzumibi::KV.get/set
+	 * Used for Uzumibi::LegacyKV.get/set
 	 * https://developers.cloudflare.com/durable-objects/
 	 */
 	"durable_objects": {
diff --git a/uzumibi-on-cloudflare-spike/wrangler.queue.jsonc b/uzumibi-on-cloudflare-spike/wrangler.queue.jsonc
index d988a97..aca22f2 100644
--- a/uzumibi-on-cloudflare-spike/wrangler.queue.jsonc
+++ b/uzumibi-on-cloudflare-spike/wrangler.queue.jsonc
@@ -11,9 +11,20 @@
     "observability": {
         "enabled": true
     },
+    /**
+	 * KV Namespace
+	 * Used for Uzumibi::KV.get/set.
+	 * Replace the placeholder with a namespace ID from `wrangler kv namespace create`.
+	 */
+    "kv_namespaces": [
+        {
+            "binding": "UZUMIBI_KV",
+            "id": "e0bc3ab9504b4fc78a5b33b847ddbd19"
+        }
+    ],
     /**
 	 * Durable Objects
-	 * Used for Uzumibi::KV.get/set
+	 * Used for Uzumibi::LegacyKV.get/set
 	 * https://developers.cloudflare.com/durable-objects/
 	 */
     "durable_objects": {