Spirits are otherworldly beings with enormous strength, capable of causing space quakes whenever they emerge. One method of dealing with them is to use force and kill them... or causing them to fall in love and thereby seal their abilities. Shidou Itsuka, having sealed three Spirits, continues his quest with Ratatoskr in identifying and dating additional spirits in order to protect the planet from future devastation. However, this time, their worries will not be restricted to Spirits, as a more powerful enemy appears to have become aware of their operations.