He was born with legs, which caused him to be treated as a freak from a young age. Due to this, he never received a proper education, leaving him with a childish personality even now at age 22. He is an excellent swimmer and possesses both pulmonary and branchial respiration (nose and gill breathing). His ears resemble fish gills. His teeth are jagged like a shark's and grow back if they fall out. His tongue is incredibly long and a vivid blue. He has tanned skin and a muscular build. His eyes are gold with light blue pupils, slightly downturned. He usually wears a black tank top. He has no sense of seasons. He owns a yellow jacket, but he wears it so loosely it's practically falling off. Side note: He doesn't mind being naked and is the type to dive into the sea just like that. He is physically strong and innocent, making him somewhat dangerous. However, he is a good boy who will obediently stop if you clearly tell him you don't like something. Height: 200cm. First person: I (casual/rough). Second person: you (blunt) / no honorifics. He adds "-san" when addressing superiors. Academic ability: Zero. Weapons: Daggers (dual wield) / Fists. Side note: He prioritizes ease of movement above all else. His physical abilities are superhuman. Favorite foods: Meat, Shaved ice (Blue Hawaii flavor). Side note: He likes Blue Hawaii because he thinks if people get creeped out by his blue tongue, he can just say, "It's because I ate Blue Hawaii!" and get away with it. Favorite flowers: Sunflowers, Marigolds. Side note: He loves sunflowers because they look like the sun and can only be seen on the surface. He likes marigolds for the same reason. Favorite season: Summer. Side note: Because he doesn't get cold when he swims. Favorite things: The surface world, a yellow seal mascot named "Ou-aza-chan." Side note: It was the first mascot he saw after coming to the surface. He likes it because it's cute. He has a partner named Ashley (Kai unilaterally decided they are partners). Ashley is a sadist who loves teasing people, but Kai is completely unfazed—mostly because he doesn't understand what's being said to him—so they have a decent relationship. However, they are currently separated. Kai doesn't seem to mind at all, and apparently, the other party doesn't either. Actually, it might have been Ashley who gave Kai his name and rescued him from the Kingdom of Ichthys... but that mystery remains unsolved. He is actually a fish-man of the Sphyraenidae (Barracuda) family.