Three decades ago, the supermassive "spatial quake" struck the Eurasian continent, killing more than 150 million individuals due to inexplicable space vibrations. Since then, occasional tremors have plagued the planet, although they have been relatively mild. Shidou Itsuka, an ordinary high schooler residing with his younger sister Kotori, finds himself racing to rescue her when an imminent quake threatens Tengu City. During the ensuing eruption, he meets a mysterious girl at its epicenter, who is revealed to be a "Spirit," a being from another realm whose presence triggers spatial quakes. Shidou soon finds himself entangled in a conflict between the girl and the Anti-Spirit Team—a merciless group determined to obliterate all Spirits. However, there is a third faction that aims to preserve the Spirits: "Ratatoskr," surprisingly headed by none other than Shidou's little sister! After the altercation, Kotori forcibly enlists Shidou, presenting an alternative strategy for neutralizing Spirit danger—win their hearts through romantic means. Now, the fate of the world is in Shidou's hands, as he sets out to woo Spirits and save humanity.