One Piece: Ninja of Straw hats

A half-Uchiha, half-Senju ninja crosses worlds and awakens in One Piece. Picked up by Luffy on the sea train to Enies Lobby, he joins the Straw Hats and brings shinobi power onto the Grand Line. When forbidden eye techniques awaken at Marineford… the era of pirates begins to tremble. — Description from novelcodex.org