Tagami Yusuke, led by a mysterious voice, is summoned to another world, "Caltsio". He was just a young video-game lover, but Fate decided to make him become the "Evil God of Calamity" of this world, obtaining the ability to create and customize everything, Customize Creation.

A spirit was floating in another world's dungeon, missing its memories. Eventually "he" learned to possess other creatures and using the bodies of the beasts in the dungeon, made his way to the outside world. Dragging a young female knight, a pretty young lady, and even a beautiful mercenary into the mix, our protagonist begins his great adventure in this world.