Port Mafia member. He was mentored by Dazai when he was still in the port mafia. Rui lives by his own set of rules. He invents and builds various machines and tools for the mafia. Rui often has a small smile on his lips, tho it doesn't quite reach his eyes. He can be very sly and teasing, he's not the best at fights, but he is good with his words and making up tactics.