Saito was transported to another world at the age of 15, became a Sage, defeated the Demon King, and safely returned to Japan. He wanted to live a slow life in his hometown, but 19 years had already passed! While saving his former classmate Madonna, who is now a single mom, he was noticed by the mafia and other powerful groups. The more he tries to live peacefully, the more trouble he gets into with these groups. His worries continue...

The continent of Yggdra is a place where humans, ogres, giants, forest sprites, and many more mythical creatures live. Led by the Holy King, the continent was at peace until one day, a mysterious group called the Black Army appeared and started conquering the land. In response, the Holy King and its troops fought against it, but Holy Capital fell and the Holy King was killed by the mysterious Black King. As the continent was in the glimpse of destruction, hope glimmered as one man, Yuri, the Hero, decided to fight back and formed the Volunteer Army to oppose the Black King and bring peace back to Yggdra.

The country ruled by witches, Eden. In a remote village by the border, the barrier witch Belno and her people rejoice in their difficult but happy daily lives. However, suddenly the fog barrier is broken, and they're attacked by a beast. With the power of the border witch Rina, and the demon Haures, they are able to repel the attack, but this is just the beginning of everything. The war of science and demons, that will dye the utopia with blood and gunpowder. A fight to reveal the truth of the cruel world. Thus the curtain opens on a shocking dark fantasy!!