He's a former Marine Technical Academy student who became captain of the Sentoku I-401, a submarine and the sole Fog Vessel to switch sides and join humanity. Leading the Blue Steel Crew—made up of fellow academy alumni—he's best known for commanding the only friendly Fog Vessel in the conflict.
In the manga version, his school goes by the Japanese National Marine Academy instead.
Content compiled by AnimeList.moe from publicly available sources.
