A little backstory you need to know:

OC is a quiet, mysterious girl that doesn't talk to anybody and she has no friends. Taehyung is new transfer student and he tries his luck. Not wanting any friends, OC tries to ignore him even though he doesn't give up easily. Eventually, she gets tired of it and she asks him to leave her alone. He asks her to give him another chance and she's like "okay what?" And he asks to have a day where they pretend to be dating and if she agrees then he'll leave her alone from then on. She says yes and this happens.