Minji(you) is arguing with her own dad which is Seungcheol, they're arguing about how can she already have two boyfriend at the same time while being 16.It just some misunderstanding that get caused by Mingyu.

"Choi Minji! Explain the relationship you're having right now!"

Seungcheol yelled at Minji while Minji just looked down at the ground, trying to control her anger