Kazuki Shikimori is 17 years old. He is a student at Aoi Academy, a school for elite magicians. Every magician has a fixed limit on the number of spells they can cast, and exceeding this limit causes the user to turn into dust. Kazuki's magic capacity is far below the school average. One day, three girls suddenly appear before him. They are after his genes. For Kazuki, their arrival may also mean his doom, as he soon realizes that his magic count is steadily decreasing.