Gaku Mikawajima (三河島學, Mikawajima Gaku) (or Gatcho, がく) is a student at the Mikageyama Grade School and is a friend of Taichi and Toshimori. They are all taught by Toshimori's Teacher. His nickname might also be represented by the spelling Gaccho and his name might also be spelled Jimagaku Mikawa.