Sakumiya Minagi and his adopted older brother Amou live in a family which protects the katana "Kiriyasha" and "Hagasumi." Kiriyasha has been known to be attracted to blood and the only thing that can stop it is the sword "Hagasumi." After the death of Minagi's father, strange people start to appear around Minagi, some attacking him and others protecting him. Soon after, his brother Amou breaks the seal of the Kiriyasha and leaves the Sakumiya house after killing his mother. Minagi now has to fight his brother with the Hagasumi and seal the Kiriyasha once again.