With the onset of the approaching second spring, siblings Tatsuya and Miyuki, a diligent older brother and a top-performing younger sister, complete their initial year at a magical high school. During their spring break at a villa in the Ogasawara Island chain, their tranquility is disrupted by the unexpected arrival of Kokoa, a solitary young woman who has fled the Naval base, confiding in Tatsuya with a heartfelt desire.