diff --git a/twiq/.gitignore b/twiq/.gitignore
new file mode 100644
index 00000000..b83d2226
--- /dev/null
+++ b/twiq/.gitignore
@@ -0,0 +1 @@
+/target/
diff --git a/twiq/Cargo.lock b/twiq/Cargo.lock
new file mode 100644
index 00000000..8bc3d060
--- /dev/null
+++ b/twiq/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "domain"
+version = "0.0.0"
diff --git a/twiq/Cargo.toml b/twiq/Cargo.toml
new file mode 100644
index 00000000..c66a4d73
--- /dev/null
+++ b/twiq/Cargo.toml
@@ -0,0 +1,2 @@
+[workspace]
+members = ["crates/*"]
diff --git a/twiq/crates/domain/Cargo.toml b/twiq/crates/domain/Cargo.toml
new file mode 100644
index 00000000..ef157592
--- /dev/null
+++ b/twiq/crates/domain/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "domain"
+version = "0.0.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/twiq/crates/domain/README.md b/twiq/crates/domain/README.md
new file mode 100644
index 00000000..c69e3e55
--- /dev/null
+++ b/twiq/crates/domain/README.md
@@ -0,0 +1,61 @@
+# domain
+
+## メモ
+
+- Twitter にリクエストを投げてレスポンスを保存する
+- レスポンスから何を得ておくべきか
+- リツイートの扱いをどうすべきか
+- 画像の扱いをどうすべきか
+
+```rust
+// application layer
+let created = request_repository.find_created();
+let started = created.start();
+request_repository.store(started);
+
+let response = service.send_request(started);
+
+let finished = started.finish(response);
+request_repository.store(finished);
+```
+
+```mermaid
+classDiagram
+  class Created {
+    at : Instant
+    start() Started
+  }
+
+  class Started {
+    created : Created
+    at : Instant
+    from(Created)$ Started
+    finish(Response) Finished
+  }
+
+  class Finished {
+    started : Started
+    response : Response
+    at : Instant
+    from(Started)$ Finished
+  }
+```
+
+```mermaid
+stateDiagram-v2
+  [*] --> created
+  created --> started
+  started --> finished
+  finished --> [*]
+```
+
+## モジュール構造
+
+- aggregate ... 集約
+  - attr      ... 属性
+  - entity    ... エンティティ
+  - error     ... エラー
+  - event     ... イベント
+  - value     ... 値
+- event     ... イベント
+- value     ... (集約をまたぐ) 値
diff --git a/twiq/crates/domain/src/lib.rs b/twiq/crates/domain/src/lib.rs
new file mode 100644
index 00000000..1b4a90c9
--- /dev/null
+++ b/twiq/crates/domain/src/lib.rs
@@ -0,0 +1,8 @@
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        let result = 2 + 2;
+        assert_eq!(result, 4);
+    }
+}