Chiaki is 16 and is a new student who also lives in the same apartment complex as Maron (in the apartment next door) and is also in Maron's and Miyako's class. He ran away from home because of something he wanted to do. Like Maron, Chiaki also has an alter ego, which is Kaitou Sinbad. He also has the ability to seal demons using pins, like Jeanne. Although he always seemed to go against Maron (at first), he does it for a reason. He also knew about Maron's true identity. In the manga instead of using pins to seal demons, he used daggers. Chiaki is a "ladies man", or "womanizer" and always tries to seduce Maron, who at first, can't stand him and his habit of always trying to protect her. At first he says he was just trying to get closer but later he says he wants to protect her forever.