Hiroya, a rookie office worker in a trading company, is suddenly reincarnated into another world along with his female boss, Kazumi. At the age of 8, his memories of his previous life return.

This new world is a fantasy land filled with swords, magic, and monsters. Hiroya lives as the second son of a noble family in a rural town, while Kazumi becomes the daughter of a knight protecting the town. The story follows their growing bond in this magical world.