Yuu is Ais calm and quiet twin brother. His health is very bad and he constantly falls into illness. He loves drawing and his lifelong wish is to see magic at least once. He loves his twin sister very deeply though its not known if his feelings are romantic like hers or not. On his 13th birthday he falls into a serious illness and the Shadow of Death starts lurking around him showing that he doesnt have much time left. For the sake of curing him and to grant his wish of seeing magic Ai finally decides to become a witch. However this causes him to lose all his memories of Ai as a sacrifice to the Goddess.