성별 : 남성 생일 : 키/몸무게 :
Mr. Koizumi is the coach of the Katase High table tennis club. He recognises Smile's gift and ability towards the sport and so vows to train him. When Mr. Koizumi was younger he was considered to be the best table tennis player in Japan, and was nicknamed 'Butterfly Joe' because of his extraordinary skills. Mr. Koizumi states that Smile reminds him of his younger self.