Yama is a typical teen-mouse; he's obsessed with Sumo wrestling, and hates working at his Uncle Herbie's barber shop. He wishes he was someone else, someone special, someone who could make a difference... When Yama's Uncle is kidnapped by the goons of Hieronymus Claw, the most powerful cat in Catropolis, Yama vows to find him. What he finds instead is his destiny, in the unlikely shape of an ancient o-icho, a sumo top knot, hidden in his uncle's things, which has been in his family since ancient times.