A stray cat wanders into a sumo wrestler's gym, and instead of chase him away, the wrestlers bring him in in exchange for chasing away the mice that frequent the gym. Over time the cat gets fat and can't chase mice, thus getting put back outside. But the main wrestler is afraid of mice so he trains the cat in the ways of sumo. Soon, the cat defeats the mice, giving the wrestler the courage to defeat his own nemesis. Includes Japanese sumo terms throughout.