College student Kousuke leads an ordinary life filled with video games, yet he is haunted by vivid nightmares of transforming into a demonic force. His routine is shattered when the goddess Fauna manifests before him, intent on eliminating the evil power lurking within. Instead of destruction, she proposes an intimate alliance with herself and her sister Jordh to contain the threat. However, the arrival of the mischievous devil Natsuki threatens to complicate their plans from the very beginning.