Busou Renkin Summary

Summary
One night Kasuki Muto tries to save a girl from a monster, but gets impaled through the heart. The next day he wakes to find that it was only a dream. That is until he finds out that it is all true when a creature called a Homonculus attacks him and his sister. The girl, Tokiko, Kasuki saved the night before comes and fights the creature. Kasuki finds out Tokiko is a alchemic warrior and that he did in fact die but Tokiko put in a Kakugane in place of his heart. Now infused with his fighting spirit the Kakugane forms a Busou Renkin so Kasuki can fight the Homuculus, along with Tokiko, that prey on humans.