diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -1,12 +1,14 @@
 # Grower
-ブラウザ上で稼働する言語ランタイムのためのライブラリ（**G**eneral **R**untime **O**n **WE**b browser**R**s）
+Grower: **G**eneral **R**untime **O**n **WE**b browser**R**s
+
+A Library for development language runtimes that run on Web Browsers.
 
 ## Structures
 
 ### grower-rs
 
-言語ランタイムのうち，WebAssembly コードとして動作する部分を実装するための Rust クレート．
+A Rust crate to implement parts of Language Runtimes running as WebAssembly codes.
 
 ### grower-js
 
-言語ランタイムのうち，JavaScript コードとして動作する部分を実装するための Rust クレート．
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+A npm library to implement parts of Language Runtimes running as JavaScript codes.
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diff --git a/grower-rs/README.md b/grower-rs/README.md
new file mode 100644
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+# Grower
+Grower: **G**eneral **R**untime **O**n **WE**b browser**R**s
+
+A Library for development language runtimes that run on Web Browsers.
+
+
+## Features
+
+### core::jsni
+
+An implementation of JSNI (JavaScript Native Interface). JSNI is a FFI for a linear-memory between WebAssembly Runtimes and JavaScript Runtimes. You may use this API to call JavaScript functions from Rust. 
+
+For example:
+
+```rust
+use grower::core::jsni::*;
+
+let ni = JavaScriptNativeInterface::new();
+
+let return_values: Vec<JSNIValue> = ni.call("hogeFunc".to_string(), vec![
+    JSNIValue::from(2 as i8),
+    JSNIValue::from(1 as i16),
+    JSNIValue::from(1 as i32),
+    JSNIValue::from(1 as i64),
+    JSNIValue::from(8 as u8),
+    JSNIValue::from(16 as u16),
+    JSNIValue::from(32 as u32),
+    JSNIValue::from(64 as u64),
+    JSNIValue::from(0.5 as f32),
+    JSNIValue::from(6.4646464 as f64),
+    JSNIValue::from("hoge".to_string()),
+    JSNIValue::from(vec![1, 2, 3, 4, 5, 6, 7, 8]),
+]).await;
+```
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