Avatar Tuner, Vol. 1 (Quantum Devil Saga)

In the post-apocalyptic
Junkyard, a mysterious religious order known only as the Church watches over the
brutal competition between warring tribes as they vie to unify six territories
and thereby gain access to Nirvana, the promised land. In the wake of one
particularly unusual battle, Serph, the leader of the upstart Embryon tribe,
rescues a strange girl and discovers that he and his fellow fighters have
gained the ability to transform into terrifying demon warriors. But these new abilities,