Revenge / Seoyeun Lee

A Kungfu-master is industriously exercising kungfu.
Even while eating he can't stop.
An angry Ninja-fly occurs Ten years later in front of the Master.
The old Master does not realise the tiny fly.
Suddenly he gets deadly hit by Ninja-stars aimed by the fly.
Ten years ago the little Baby-fly is playing on top of a Tofu.
What has only happened back then?
What reason had the revenge of the litttle fly?