Buso Renkin

On the way home from school one night, Kazuki Muto unwillingly walks in on a monster attacking a girl, and he is stabbed in the heart while trying to save her. Turns out the girl, Tokiko, is an Alchemic Warrior tasked with the duty of destroying monsters known as homunculi with her Buso Renkin (alchemic weapon), Valkyrie Skirt. In order to save Kazuki’s life, Tokiko inserts an alchemic device—a Kakugane