Gonzaemon Kato was captain of the Bentenmaru until his supposed death from food poisoning—an event that kicks off the whole series by forcing his daughter Marika to take over the ship. But he's not really gone. In the anime, it's revealed he faked the whole thing and went underground as an imperial pirate operating under the alias Ironbeard.
The Katos come from a storied line of military and pirate service. Gonzaemon himself started as a naval officer before commanding the Bentenmaru. He married Ririka at some point, though she eventually left him to raise Marika alone.
Content compiled by AnimeList.moe from publicly available sources.
