Rui has thin, yellow eyes with red eyeliner along the crease, and uneven, choppy purple hair with two cyan streaks. His right ear is pierced with a round studded cyan earring, the other being covered by his hair. His voice is gentle, though it becomes strained when he is excited or curious. 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. His smile is described as like a cat's.