busou renkin [Manga]

Kazuki Muto, who saves Tokiko Tsumura and is killed by an alchemical monster known as a homunculus. Tokiko, an alchemist warrior, feels responsible and revives him by replacing his destroyed heart with a kakugane. The kakugane is an alchemical device which, when activated, takes a weapon form based on its user’s personality, forming a buso renkin—the only thing that can destroy a homunculus. Kazuki creates his own buso renkin and joins Tokiko in the fight against the homunculi and their master, Koushaku Chouno.