Miyazaki, Ryuu

The president of Kazuki's class. He is considered to be a reliable and exemplary student.

[Spoiler] It is later revealed that he is Riko Asami's brother, as well as the killer of his divorced mother, and their new mother. He helps Riko, who hated her life and wanted to replace Kazuki as the one who is close to Maria, possess Kazuki's body through setting up situations where they can ruin Kazuki's life when he is possessed. Eventually, though the brother admits to the murder of their divorced mother and her new lover, the siblings realize they still have each other despite their mentally torn family. Riko willingly gives up the box, and Miyazaki is sentenced to prison for murder. [/Spoiler]

(source: Baka-tsuki)