Genryusai D. Koga (元柳斎･D･鋼牙 Genryūsai D. Kōga?) is a Marine, Vice Admiral who was trained under the supervision of both the Former Marine Admiral, Aokiji and Vice Admiral, Tsuru and is the main protagonist of the One Piece, Spin-Off, Rebel On. He is the son of Genryusai Raiga a former Marine Rear Admiral who defected from the Marine two months prior to the Death of the Pirate King twenty four years ago and Kagame D. Shizuka a Former Infamous Pirate Captain of the New World.