Iruka is a pink and white dolphin. He has blue eyes, bushy black eyebrows and wears a black tie around his neck. Due to his need for water, he is almost always seen inside an aquarium or a mobile water tank. If he is deprived of water, he will slowly change colors until he turns grey, at which point he runs the risk of dying.
Iruka is very enthusiastic about teaching, sometimes to the point of exasperating his students. His hot-blooded nature means he will push his students to the extreme and get angry at them for not listening, and he often employs corporal punishment in the form of his Dolphin Kick, though he's overall a good-natured and determined teacher.
- "Iruka" means dolphin in Japanese, befitting to his name.