Buso Renkin

Buso Renkin is an anime about a teenage boy, Muto Kazuki, who becomes involved in a world of Homunculus (Homunculi)and alchemy when he saves a girl's life, Tokiko Tsumura, at the cost of his own, she replaces his heart with a Kakugane and he then decides to become a destroyer of the homunculus. 武装錬金