Ryuuki Senoo is a side character in the series Hokenshitsu no Shinigami (保健室の死神').Edit
He appears to be a hotblooded delinquent with few penchants against getting into fights and speaking to or treating everyone he meets roughly. When he was first introduced, Ryuuki harbored a strong dislike of the female sex and believed with conviction that any and every specimen would treat a member of the male sex poorly. This seems to have stemmed from the relationship he holds with this three elder sisters Koko, Suzume and Tatsumi, who treat him like all but a slave (although they do seem to be fond of him) and leave any housework that is necessary in his hands without making an effort to help him.
However, after being possessed by a Byouma(disease demon) and going on quite the rampage through the middle school Hades-sensei teaches at, he has an encounter with Kaburagi Maya and decides to become somewhat her disciple or lackey; he even goes as far as transferring into her school. In the chapters since, Ryuuki's dislike of women seems to have faded somewhat, as he has developed some civil rapport with several female characters, but his relationship with his sisters still remains about the same. It does not appear that there are parents present in Ryuuki's household.
Ryuuki is both overenergetic and overzealous about most things, and his rough attitude has earned more than one startled or wary reaction, but it is evident that he cares deeply for the people around him and harbors a strong loyalty for his friends; he also appears to be extremely driven. At a point when his friend Kaburagi Touya began behaving strangely and went missing due to the influence of a disease demon, Ryuuki both tried to talk sense into him and help him, and went looking for him when he disappeared. Hades-sensei made an observation that Ryuuki had been very worried about Touya.
Although he appears to be rather close friends with Kaburagi Touya, Touya's attitude toward him is often exasperated or irritated; however he does not push Ryuuki away, implying that he does not actually dislike him. It has also been implied that Ryuuki may have a bit of a crush on Touya's elder sister Maya, whom he refers to as his "onee-san." This is extremely ambiguous however. One sure thing is that Ryuuki hopes to reach a point one day where he is stronger than Maya in martial arts, and he seems to work very hard to reach that goal.