Walpurgis Night

Walpurgis Night (魔女たちの夜 (ヴァルプルギス),) is a great "event" referring to the war between Tower Witches and Workshop Witches because of the white princess sealed inside Honoka Takamiya. It was first mentioned in Chapter 3.

Trivia

 * "Walpurgis Night" might reference the event with the same name, which was held in North Europe to celebrate the season of Spring.