MAY CONTAIN SPOILERS:

Chizuna's younger brother. Recently afflicted by a "vampiric" condition that is passed down through the Takashiro family. He has his mother's last name. At the first of the manga series, he admits to himself he's in love with Yaegashi, but later pushes her away after he has a dream in which he killed her for her blood. As Kazuna showly cuts ties with Yaegashi, he begins to fall in love with his sister. The two even kiss (once in the anime, twice in the manga). For his disease Chizuna gives him two bottles, one of a serum that gives her some relief, and one for suicide, if it becomes too much. At the end, with Chizuna near death, he declares that he will take the suicide medicine, because he can't think of living on after she dies. Later both are shown unconscious on the floor of Chizuna's bedroom. In the anime he dies. In the manga, in the next chapter he is shown in the hospital, with no memory of what has happened in the past year. According to Chizuna, he looks like their father.

(Source: Wikipedia)