Dumbeast (2009)

An editor arrives at a Sumo village to find the missing award-nominated writer Deko just in time to bring him to an award ceremony. There, the editor learns that Deko's weird friends have been desperately trying to kill him because of the book Deko wrote about their embarrassing memories. Despite their countless attempts at murder, Deko's dumbness keeps him from even noticing his friends' intentions.