Chika Fujiwara

The secretary of the Shuchiin Academy student council. She could not be predicted, her thoughts could not be read. A natural disaster who unconsciously threw everything into chaos simply by being present, also known as Subject F.

Spoiler

In chapter 222 of the manga, Chika reveals that she played piano because she wanted to be perfect, and she becomes a prodigy at the piano. The expectations of her family and her fans rose, forcing her to practice more. She quit piano after Kaguya told her to just quit if she didn't like the piano. Soon after Chika challenged Kaguya to a game battle and if she won, she would get to become Kaguya's friend. In the end, she becomes Kaguya's first friend.