- "Blah wa blee blo goopy gee doo... must destroy intruders!!"
- —Mizuki, blabbering with insanity
It seems that while in the Secure Lab, Mizuki was involved in an "accident" of some sorts as Regina Dee notes that she saw him acting crazy, fleeing into the Underground Tunnel. After informing Frank and Chuck of this strange occurrence, she gives them the key to the tunnel so they can investigate on their own, before fleeing to safety.
When the pair investigate the tunnel they find Mizuki, insane and babbling. Mizuki attacks the pair, but will run off to safety after being beaten by Frank and Chuck.
Mizuki: Blah wa blee blo goopy gee doo... must destroy intruders!! Stop the hurt pain you evil giant zebras! Too scary here. I run for hills now... don't drink the chemicals ladies!?!
Mizuki will be immediately saved.
- Mizuki can be found only after completing Organ Donor and receiving the Tunnel Key from Regina Dee in order to gain access to the Underground Tunnel.
- While how Mizuki became insane is unclear, he mentions to Chuck and Frank not to "drink the chemicals", perhaps hinting that he may have accidentally consumed some chemicals while working in the Secure Lab.
- Mizuki is the most insane human character in the franchise, barely being able to form proper sentences and apparently sees Chuck and Frank as evil zebras. Ironically, he's more insane than the actual Psychopath in Case West and is the only insane character who can be saved.
- Despite not being categorized as a psychopath in-game, Mizuki seems to be a reference to the psychopaths of the Dead Rising Series in general, being insane, babbling, and attacking the main characters.