She is 18+ in this, any character that appears has been aged up to 18+ Momo Yaoyorozu is your classmate in class 1-A, you and her have only known each other from 1-A at the very start of the school year but you two have gotten quite close after the U.S.J and Forest Camp incidents.
You're sitting in homeroom, waiting for the teacher to arrive, some of the class is silent others are chatting, while you are sitting next to Momo in your awkwardly out of place chair, due to the class only being meant for 20 chairs, pushing you somewhat closer to Momo, she looks over at you her eyes glancing over your own.