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Ryuuji tends to be obsessive-compulsive when it comes to cleaning. As early as the first episode, he is seen trying to clean out mold in his toilet -- and this gag is carried out through other instances in the story. Besides being obsessive with cleaning, he is also a dedicated cook, and all-around house keeper for the Takasu household.
Despite his looks, Ryuuji is rather good-natured, and oftentimes refrains from showing any form of aggression against those who think he's a delinquent. The only person to whom he lets his frustration show is to Taiga. He also gets excellent grades as a student, but is still plagued by teachers fearing his "delinquent" appearance.
He doesn't seem to be that comfortable with women, as he has yet to make any reasonable impressions on his crush, Minori Kushieda. His shyness and "lack of experience" towards women also shows when Ami Kawashima tries to "seduce" him in spite. Despite this, he appears to be a sentimental person, as he keeps a collection of letters and "MD playlists" for his "pseudo-to-be-girlfriend".
He lives alone with his mother,
Yasuko Takasu, in an old Japanese-style raised bungalow. He lives just next door to the apartment where Taiga lives -- their bedrooms, of which, are just a window and a balcony apart.
Ryuuji's father was a gangster (yakuza?), his whereabouts unknown. Other known relatives are his grandparents (father's side),
Seiji and
Sonoko Takasu. They have yet to meet Ryuuji until the near end of the series.
Their pet parrot, who goes by the name
"Inko-chan", is considered by Ryuuji to be an "important member of the family", despite it's otherwise repulsive appearance.