Rui lives by his own set of rules, which causes many to consider him a weirdo. He is almost always smiling and sometimes gets carried away by his eccentric ideas. Despite the apparent riskiness of his ideas, Rui does his best to take safety into consideration. In the event It's On! Wonder Halloween!, Rui becomes deeply concerned about Tsukasa's safety, and subconsciously holds himself back as a result. Rui also has levels of curiosity that borderline on obsession, as he loves to take toys apart.