Maburaho

A 17-year-old student named Kazuki Shikimori goes to Aoi Academy, a school for top magicians. Every magician has a set number of spells they can use, and exceeding this limit can result in turning into dust. Kazuki's magic limit is much lower than most of his classmates. One day, three girls suddenly appear and express interest in his genes. Kazuki soon notices that his magic limit is steadily decreasing, which could be dangerous for him.