A hungry cat gets a job hunting mice at a sumo training center (heya), but once the mice are gone he continues to stuff himself until he is too fat to chase the mice that have returned--so he decides to train with the sumo wrestlers, and SumoKitty becomes a scourge of mice and an inspiration to the wrestlers.

"Sumo Joe and his friends pretend to be sumo wrestlers, but when his little sister who takes Aikido wants to join them, Sumo Joe must choose between his friends and his sister. Includes author's note about sumo and aikido, and illustrated glossary"-- Provided by publisher.