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 also has levels of curiosity that borderline on obsession, as he loves to take toys and home appliances apart to see how they work.