In a time when the great war between five rival races for supremacy on Earth ended with humanity's victory led by the hero Sid, the world suddenly gets "overwritten" right before the eyes of a boy named Kai. In this rewritten world, Kai witnesses humanity's defeat in the war as a result of Sid's absence—where dragons and demons now rule the land, and Kai himself has become a forgotten existence to all humans. However, after encountering the mysterious girl Rinne, Kai resolves to break free from this rewritten fate. In a world without a hero, he inherits the sword and martial skills of the hero (Sid) and challenges the powerful enemy races that dominate the land. (Source: MAL News)

Najimu Mujina is just your average five-year-old girl—who also happens to be the CEO of Mujina company. While she leaves most of the important work to her secretary Yuki Karuizawa, she often tries to act like a CEO with her inadequate business jargon. But, although her innocent efforts can be unexpectedly kind and uplifting, it just usually adds to the troubles of those around her, such as diligent employee Mayu Warito and her fellow colleagues at Mujina Company.