Height 143 cm; 173 cm Attended Iwatobi Junior High School with Haru and Makoto, was in the same class as Asahi, Kisumi and Haru. Was in the swimming club with Haru, Makoto and Asahi. Natsuya's little brother. Left to America with him during junior high school days. He is an excellent swimmer, but has health issues due to his perfectionism and over-training. Swims breaststroke and individual medley.

Spoiler

Ikuya's health is fragile, and he has some fear of water due to the fact that he nearly drowns several times. Yet, being a determined athlete and not wishing to disappoint his brother, he pushes himself endlessly, often suffering from oxygen deprivation from over-training in the pool. This drive is due to his belief that swimming and competition are to be mastered, as indicated by the anime's depiction of water being an "enemy" that binds him. In this way, he is shown to be both similar to and different from Haru - both genius swimmers with radically different approaches to their sport.