Kiraware Yuusha wo Enjita Ore wa, Nazeka Last Boss ni Sukarete Issho ni Seikatsu shitemasu!

Just before the battle against the demon god "Demiurge" that destroys the world, the hero Ares is hated by his friends and is left alone. In fact, it was because he couldn't make his friends to join him in the fight against the last boss who might not make it out alive, so he dared to play the role of the hated one to get them to leave him. Ares, who had to fight Demiurge alone, was supposed to restore to peace in exchange for his life... but somehow he is still alive, and next to him is the Last Boss. Before he knows it, she has fallen in love with him, and Ares begins to live his life trying to save the world!

(Source: Hifumi Shobo)