Ryoki Tachibana

Hatsumi's biggest fear since she was a child, due to him pushing her down the stairs. He turns Hatsumi into his personal slave, but also wants her as his girlfriend. Although he seems to be a complete jerk to her, there are times when he lets his guard down and cares about her and ends up falling in love. At the beginning of the series, he is a second-year student at the prestigious private school, Kaisei Academy. It is revealed that when Hatsumi and Ryoki were kids in the company housing complex, that Hatsumi was Ryoki's sole friend, while Hatsumi was also friends with Azusa. Nevertheless, Ryoki did not treat Hatsumi well, even as children, going as far as pushing Hatsumi down a flight of stairs, emotionally scarring her. This was revealed later to be an unintentional accident. (from Wikipedia)