He is a happy-go-lucky guy who is Kazuma's best friend as well as his neighbor. He is also Teppei's kindergarten teacher and is one of the few people who know about Kazuma and Fumino's marriage. Ryū takes care of Teppei a great deal (while Kazuma and Fumino are being lovey-dovey), and also poses as Fumino's distant relation and guardian, which is their official lie to conceal the relationship between the two.