Because It's the First Time (처음이라서 / Cheo-eumiraseo)

Yoon Tae Oh (Choi Min Ho) is a free-spirited college freshman who hosts his rooftop as a hideout of sorts for his five friends. Amongst this diverse group is his childhood friend, Han Song Yi (Park So Dam). As Tae Oh starts to fall for Song Yi, another friend, Seo Ji An (Kim Min Jae) starts to develop feelings for Song Yi as well.