A star baseball player at the Kisaragi Boys' High School and son of a wealthy family, he was being groomed as a potential boyfriend and possible fiancé of Izumi. However, Hiroki has an attraction to the spunky Ryo: he calls her "Ganmo-chan" ("Tofu girl" in the English dub) as it is his favorite part of oden. At the end of the series, it is strongly hinted that he and Ryo will end up together.