Shido Itsuka lives in a world where spacequakes erupt without warning, until his sister Kotori tells him what they really are: Spirits crossing into the human world. Force cannot stop a Spirit's rampage, but affection can, so Shido is recruited to date them one by one, starting with the sword-wielding girl he meets in the rubble and names Tohka. Koushi Tachibana's light novel series follows him through that first attempt and the organization Ratatoskr standing behind it.