Koichi Hikarino, a young man born in Japan but raised in Germany due to his father's job, lives a tranquil life as a third-year high school student alongside his three friends. However, one day, he inadvertently lost a bet against his friends. As a consequence, he now finds himself in the present moment, facing the punishment of venturing alone into a vast abandoned mansion. Rumors swirl about the mansion, suggesting it harbors a beautiful yet violent vampire within its dark confines.