The heroine's only relative, the sudden death of her grandfather, the mysterious death of her pet dog, the accidental death of her friend, and the same nightmare every night. Just when she gradually regained her happiness in the company of her friends and classmates, the nightmare of the end of the world came again. From then on, the heroine and her teammates embarked on the road to becoming stronger, and unexpectedly developed their own and their companions' strange abilities.