Rei Kuroi (黒井レイ) is a student of Sankai High.
He was attracted to Annette, though she is not his teacher. While wearing glasses and a sick mask, he bought a witch hat and cloak that she was selling at a yard sell, and joyously tried them on with the happy thought of having clothes that belonged to her, although they actually belong to her grandmother. Little did they both know that this outfit renders the wearer invisible, and he soon found out that he was unable to remove the outfit, hence he returned to Annette to ask for her help, who instead drove him away whenever she saw his face looming in the darkness, believing she’s being stalked. The next day, she negotiated with Rinne to get rid of Rei, calling him the neck man, but he realizes Rei’s not a ghost and his problem is learned. However, Annette was inefficient and not even Tsubasa’s skills could help in getting Rei undressed, but Rinne finds a card written in French tucked in the hat's band, that Annette herself can’t even read, and her grandmother just happens to return home and say the simple phrase “Costume Enleve-toi!” (Costume, Come Off!), freeing the young man. After being hit in the head by her grandmother, Annette promised Rei a date, but she purposely stood him up.