The hero Ares was about to fight the final battle for the fate of the world. However, the three party members who became his friends on the trip said, "I can't follow you anymore!" Yes, he was hated by all the party members. Their patience had run out and they finally left Ares. But that is what Ares, the hero, wanted. The last opponent is the genie [Demiurge] who is bringing destruction and chaos to the world. He cannot involve his party members in a fight from which they may not return alive. So it was his plan to play a disgusting person who would drive everyone away from him. Alone, the hero entered the final battle, and died… or did he? Eh? Am I alive? Why am I naked? And why is [Demiurge] sleeping next to me? What happened? I can’t remember?!

The hero who thought he was dead is loved by the girl who was the ‘Last Boss’ and living with her?!

As the Soviet Union marches on Berlin in May of 1945, a secretive group of sorcerers and madmen gathers to perform a terrible ritual. They care nothing for the fate of the Reich. To them, the countless lives lost in the battle are the perfect sacrifice to fuel their spell. After the war, they vanish and are not heard from again, except in rumor. One day, it is whispered, they will return. And on that day, the world will end. Fear the demons in human form. Fear the Longinus Dreizehn Orden.

Flash forward to present-day Japan. Fujii Ren is released from the hospital after two months spent recovering from wounds suffered in a vicious brawl with his best friend Shiro. As Christmas approaches, he tries to rebuild his life, clinging to what brilliance remains. But even that is soon threatened. For the knights of the LDO have returned, and brought the apocalypse to his doorstep. Forced to wield the same unholy power as his foes, will Ren be able to protect what is dear to him from the inhuman might of the Longinus Dreizehn Orden?