The leader of the U-17 Japan team, bearing the No. 1 badge. Byoudouin is extremely aggressive and contemptuous towards the weak, which frequently puts him at odds with the more compassionate Oni. This nature came about when Byoudouin first lost to Oni in a match, but then amplified when Byoudouin protected Duke's younger sister from a collapsing roof. The injuries sustained from the accident made Byoudouin lose the subsequent match in a group league, forcing his team to drop out. The team blamed Byoudouin for the team's loss, and Byoudouin has since become bitter about any notion of self-sacrifice. Nevertheless, Byoudouin respects those that are truly strong and very much desires for the Japan team to reach the top of the tennis world. On the court, Byoudouin is known as the "Pirate of Japan" and uses a wide variety of techniques based on various cultures, even announcing their names in their native language when he uses them. Like Ryoma and Oni, Byoudouin has the aura of a ghost pirate when playing seriously, though his ability manifested only recently. Byoudouin likes to directly attack his opponents with his shots, much like Kirihara, and would often force his opponents to retire from competitive tennis permanently if they were not physically and mentally prepared to take such a beating.