|“||Short for "Wicca Institute." An association dedicated to the worship of spirits, which Hinoe was a part of. Their goal is to commune with spirits and live as one with nature.||”|
— Encyclopedia Obscura Entry
The Wicca Institute (ウィッカ・インスティテュート Wikka Insutityūto ), abbreviated to simply W.I., is an organization that worships spirits. Their goal is to commune with spirits and live as one with nature. Most, if not all members of this organization are female and regard to each other as "W.I. sisters".
- A common trait between the two known members of the organisation is an opal gem necklace that both Hinoe and Mirai wear. It might be a sign of the organisation or a spiritual item given to each member.