Ginpun

Gin Pun is the head of the Bureau of Magic, and a world-class magic user. Oyamada asks her for assistance after the incident with Mitsuko causes Yume to not be able to use her magic properly. She decides that Yume's graduation exam would consist of Yume using magic on Oyamada, and encourages Yume to see the many ways in which she and her magic can help others. Gin Pun is implied to have also helped Yume's mother in similar matters.