Thirty years ago, a massive "spatial quake," a phenomenon involving space vibrations of unknown origin, devastated the Eurasian continent and claimed over 150 million lives. Since then, these quakes have continued to occur worldwide, though on a smaller scale.
Shidou Itsuka is an ordinary high school student living with his younger sister, Kotori. When an impending spatial quake threatens Tengu City, he rushes to save her but gets caught in the eruption. At the quake's epicenter, he finds a mysterious girl who is identified as a "Spirit," a supernatural being whose appearance triggers such quakes. Soon, he is caught in a battle between the girl and the Anti-Spirit Team, a ruthless task force dedicated to eliminating Spirits.
Yet there is a third group that believes in saving the Spirits: "Ratatoskr," which, surprisingly, is commanded by Shidou's little sister! After the clash, Kotori forcibly enlists Shidou and offers him an alternative approach to handling the danger Spirits pose—make them fall in love with him. Now, the world's fate depends on his dating skills as he sets out to charm the Spirits.