Zero Infinity: Devil of Maxwell (2012)

In 1968, the city of Yahiro had undergone rapid development after the war. Ryouga lives with his imouto Takane, accepting everything that happens in life as he believes that everything in the world exists for a reason. After meeting a man Rei who did not remember anything but his own name and helping him out, they became friends. Later when Ryouga found Rei being beat up, he tried to help but instead got caught up in the battle-to-the-death world of the Imaginators, individuals who have machine hearts that make them into super-powered beings.