The school Jongdae works at gets a new teacher. Physics and Algebra teacher Dr Oh Sehun who previously taught at a university. And with each little snippet they experience throughout the day, it's not getting easier. And students can't stop themselves from shipping the two when they throw bad pickup lines at each other. Problems also ensue.

Baekhyun has had a rough childhood, but slowly his life is getting better again. He has a job he enjoys, a lot of friends to hang out with in the weekends and the best thing of all, he lives with his loving boyfriend Chanyeol. His only problem is a young man who also lives in their house, his little brother Jongin... Jongin likes to get in trouble. Doesn't listen to his teachers, smokes and drinks alcohol on the school grounds, brings home girls and guys whenever he wants