Synopsis given are according to volume numbers.

Vol 1: The Doomed

The only thing that boy genius Takara Ryuu wants, is to end his life...and the reason behind it is what new teacher and ex-officer Isamu Kazuki must find. But it seems that Ryuu's intention has changed ever since he meets this teacher, and assassins are now after him. Why? Also, Kazuki seems to recognize Ryuu's sister Ayaka from somewhere...