sentences:  During a night, Kazuki Muto, an ordinary boy, is killed by a homunculus, while trying to save Tokiko Tsumura.Feeling guilty, Tokiko, a member of the Alchemist Army, revives him by replacing his heart with an alchemical device called kakugane.The kakugane allows its wielder to form a buso renkin, a special weapon that is the only thing that can destroy a homunculus.