A wheelchair bound teenager who makes an inauspicious cameo in the last episode of the first season. He is a senior at Tenryuuin High in Shinjuku. Even with his chronic disease, Ryuuji remains an outwardly upbeat, positive, and jovial youth; he plays basketball, has many friends, and even a model-esque girlfriend. Outwardly. Despite appearances, Ryuuji is actually the second season's first antagonist.

He can control people's minds through a cellphone game that was played by Reiji Sagaya in the first season. His username in that world is Chaos (Kaosu). Ryuuji's true nature is heartless and sly; he states that he had never felt any kind of emotion - until the Chaos game, when his powers awoke after the disturbance in the Dragon Stream. Manipulating people to commit crimes proved fun for him, for a time. And then he discovered the Magami Five, watching them through the city's CCTV cameras.

Ryuuji Yashiro by name is an anime original character. In the manga, the character is known only as 過王須 (Kaosu). His real name is unknown, and he has no past memories. He is a mysterious, long-haired figure, often seen sitting in solitude; however, he is not crippled. Kaosu is kept close to Munetaka Yagyuu, and used in Yagyuu's search for the Vessel of the Golden Dragon, whom Kaosu is the Yin to.