Takuya follows his stepmother Ayumi to the isolated cliffs of Ken Point, driven by lingering worry after his father's sudden death. Concealed behind a boulder with Ayumi and her friend Mitsuki in sight, he witnesses a brilliant flash that materializes into an otherworldly woman. The stranger places an enigmatic ring on his finger, and Takuya is pulled across the threshold into a parallel realm. The artifact immediately reveals itself as the conduit linking him to shifting realities.