For the last ten-plus years, Kazuma has been seeing a repeated dream. In this dream, his younger self met a beautiful elf in the forest, who put the pendant that she was wearing in his hand and wished for him to save her daughter in the future. Even though it felt like just a dream, the pendant which he held was indeed real. However, he had never met the elf nor her daughter, and now continues to spend his days as a normal student in the boarding school Kuondai Gakuen.
One time, he noticed a blonde girl staggering about at the top of the stairs. She fainted, but he was able to catch her in the nick of time. It appeared that he was the only one who could see her. Then, he remembered one of the school’s seven mysteries: “There is an invisible girl wandering about the school.”