Humans have crafted countless worlds, each springing from the distinct imagination of its maker. Souta Mizushino is a high school student who aims to become such a creator by writing and illustrating his own light novel. One day, while watching anime for inspiration, he is briefly pulled into a fierce battle scene. Upon returning to the real world, he notices something is wrong: the anime's headstrong heroine, Selesia Yupitilia, has somehow come back with him. Soon after, other fictional characters appear in the world, bearing the hopes and scars of their origins. A princely knight, a magical girl, a ruthless brawler, and many others now fill the streets of Japan. However, the most enigmatic among them is a woman in full military regalia, dubbed "Gunpuku no Himegimi," who knows far more than she should about the creators' world. Despite this, no one knows her true name or the world she hails from. Meanwhile, Souta and Selesia team up with Meteora Österreich, a calm and composed librarian NPC, to uncover the meaning behind these unnatural events. With powerful forces at play, the once clear line between reality and imagination continues to blur, leading to a fateful meeting between creators and those they created.