diff --git a/enjo_lib/comm/method/interface.py b/enjo_lib/comm/method/interface.py
index a7b51fc..c2648d2 100644
--- a/enjo_lib/comm/method/interface.py
+++ b/enjo_lib/comm/method/interface.py
@@ -14,10 +14,6 @@ from typing import (
     TypeAlias,
 )
 
-from ...our_types import (
-    JSON,
-)
-
 
 class TransmissionSuccess(Enum):
     UNKNOWN_ERROR = auto()
@@ -25,13 +21,13 @@ class TransmissionSuccess(Enum):
     SUBMITTED_SUCCESSFULLY = auto()
 
 
-MessageHandler: TypeAlias = Callable[[JSON], Awaitable[None]]
+MessageHandler: TypeAlias = Callable[[bytes], Awaitable[None]]
 
 
 class TransportMethod(ABC):
 
     @abstractmethod
-    async def send(self, data: JSON) -> TransmissionSuccess: ...
+    async def send(self, data: bytes) -> TransmissionSuccess: ...
 
     @abstractmethod
     def on_receive(self, handler: MessageHandler) -> None:
diff --git a/enjo_lib/comm/method/internal.py b/enjo_lib/comm/method/internal.py
index f9a37aa..4bea541 100644
--- a/enjo_lib/comm/method/internal.py
+++ b/enjo_lib/comm/method/internal.py
@@ -8,7 +8,6 @@ from .interface import (
     TransportMethod,
     TransmissionSuccess,
 )
-from ...our_types import JSON
 
 
 class InternalTransport(TransportMethod):
@@ -20,7 +19,7 @@ class InternalTransport(TransportMethod):
     __recv_handler: MessageHandler | None = None
     __send_handler: MessageHandler | None = None
 
-    async def send(self, data: JSON) -> TransmissionSuccess:
+    async def send(self, data: bytes) -> TransmissionSuccess:
         if self.__send_handler is None:
             return TransmissionSuccess.EXCHANGE_UNAVAILABLE
         await self.__send_handler(data)
@@ -29,7 +28,7 @@ class InternalTransport(TransportMethod):
     def on_receive(self, handler: MessageHandler) -> None:
         self.__recv_handler = handler
 
-    async def _submit(self, data: JSON) -> None:
+    async def _submit(self, data: bytes) -> None:
         if self.__recv_handler is None:
             return
         await self.__recv_handler(data)
@@ -42,7 +41,7 @@ class InternalExchanger:
 
     __transports = set[InternalTransport]()
 
-    async def __send_handler(self, sender: InternalTransport, data: JSON) -> None:
+    async def __send_handler(self, sender: InternalTransport, data: bytes) -> None:
         async with asyncio.TaskGroup() as group:
             for receiver in self.__transports:
                 if receiver is sender:
diff --git a/test/comm/method/internal_test.py b/test/comm/method/internal_test.py
index 123e8d4..f3579d3 100644
--- a/test/comm/method/internal_test.py
+++ b/test/comm/method/internal_test.py
@@ -38,12 +38,12 @@ class InternalTransportTwoPeers(IsolatedAsyncioTestCase):
         mock_bob = AsyncCallableMock()
         peer_bob.on_receive(mock_bob)
         # send from Alice to Bob
-        await peer_alice.send("test Alice -> Bob")
+        await peer_alice.send(b"test Alice -> Bob")
         mock_alice.assert_not_called()
-        mock_bob.assert_called_once_with("test Alice -> Bob")
+        mock_bob.assert_called_once_with(b"test Alice -> Bob")
         mock_alice.reset_mock()
         mock_bob.reset_mock()
         # send from Bob to Alice
-        await peer_bob.send("test Bob -> Alice")
-        mock_alice.assert_called_once_with("test Bob -> Alice")
+        await peer_bob.send(b"test Bob -> Alice")
+        mock_alice.assert_called_once_with(b"test Bob -> Alice")
         mock_bob.assert_not_called()