Hagesawa Ko is a soon-to-be adventurer that was unwillingly reincarnated or well, swapped bodies with an 3-year-old that also was a reincarnation. Hagesawa was so powerful, life was practically a story where he had no rival. This caused Hagesawa to become depressed, but in a coincidence, his life was flipped upside-down. What could Hagesawa's new life have to offer?

On one fateful night, a boy named Kota discovers a treasury exists, left by the organization Ethos in the war with Logos six-thousand years ago. This treasury contains the greatest weapons and sorcery equipment man has ever seen. But, alas, another organization has come to attempt to take it first. If they were to get their hands on the myriad of items, it would mean the repeat of the ancient war thousands of years ago. Can Kota retrieve it before them, or will humanity pay the price?