Mad Mouse is the name of Kenji's band that he formed when he was a teenager. The band consisted of Kenji himself as the lead singer and guitarist,Haru Namio or "Charlie" as the drummer and Billy as the Bassist. Unfortunately, Haru Namio had left the band and then Kenji disbanded the Mad Mouse. However, the members reunite again in the Expo Woodstock Festival.
Revealation of the name
The name "Mad Mouse" revealed as it appeared in the band's concert ticket, which Kenji sent it to The Assasin.