In a world scarred by spatial quakes three decades ago, Shidou Itsuka, a 16-year-old living with his sister Kotori, faces the aftermath of these disasters. When caught in a spatial quake despite warnings, he encounters a mysterious girl known as a 'Spirit,' beings responsible for the calamities. Shockingly, he discovers the Anti-Spirit Team, a military group aiming to eradicate Spirits. Recruited by Ratatoskr, an organization seeking peaceful solutions, Shidou partners with his sister, now a commander, to tame these Spirits by dating them and sealing pacts with a kiss, striving to avert further chaos.