Mahoutsukai to Hoshifuru Niwa

A girl named Rio enrolls in a school for magicians and is tasked with finding a familiar. During her search, she meets Kyle, who impresses her with his kindness. On another attempt to find a familiar, she encounters Arushel, a member of an ancient demon race fleeing from the Witch of the West, who seeks to claim him. Arushel compels Rio to form a kiss contract with him to regain his powers and true form, avoiding the Witch. This angers the Witch, who punishes Rio by placing a love spell on her that causes her to transform into a boy whenever she is near someone she likes.