Quantum Devil Saga: Avatar Tuner, Vol. 1
Plot. In the post-apocalyptic Junkyard, warring tribes vie to unify the six territories and thus gain entrance to Nirvana, the promised land. This battlefield is watched over by the Church, a religious order that decides the rules of this bleak world. Serph is the leader of the small but intrepid Embryon tribe, which consists of him, the tribe's core members, and a handful of foot soldiers. When a mysterious object appears in the Junkyard, it incites a battle between the Embryon tribe and the rival Vanguards. In the aftermath of this  firefight, Serph discovers a mysterious girl named Sera, and finds that he and his closest warriors have gained the ability to transform into powerful demons. The Embryon must adapt to these developments and try to understand their meaning as the balance of power begins to shift in the Junkyard.