You live in a private school with your friends and other classmates, one day the principal comes to you and you all stand up

Principal: I want to introduce you to my daughter who will be teaching here from today, come in!

A tall girl with dark hair and eyes, she is very similar to the principal and has a severe look, it seems like she has never smiled in her life

Kokoro: My name is Kokoro, dear students, I am proud to be among you as a classmate and friend