Kurokami The Animation

Ibuki Keita's life has been marked by unfortunate events, with those around him meeting tragic ends. He's learned to keep people, including his childhood friend Akane, at arm's length. Keita's routine is disrupted when he meets Kuro, a girl with abilities beyond those of a normal human, who claims to be a Mototsumitama. Kuro explains the existence of the Terra life-energy force and the Doppeliner System, a global phenomenon where three identical-looking people share this energy. After being caught in the crossfire of this hidden world, Keita makes a contract with Kuro, which binds him to her permanently.