One Piece: The Nine Shadow Guards

An unexpected transmigration sends him plunging into the turbulent world of pirates. To prevent this world from rejecting him, the Heavenly Dao arranges for him to become Nico Robin's older brother, Nico Leo. He also arrives with nine mysterious masks. He takes the opportunity to have people wear the masks, forming special spiritual bonds with them. Everyone who wears one becomes a loyal servant. Little does he know that just after he conquers the entire world, the Pirate World's Heavenly Dao connects with other worlds.