Mr. Koizumi coaches the Katase High table tennis club. He's best known for spotting raw talent in Smile and committing to train him seriously. Back in his playing days, Koizumi was Japan's top table tennis player—skilled enough to earn the nickname "Butterfly Joe." He's said that Smile reminds him of who he used to be, which explains his investment in developing the kid's potential.
Content compiled by AnimeList.moe from publicly available sources.
