Now, Open Door!

Heavily drunk, returning student Moon Yeonsu accidentally enters the apartment downstairs on his way home, only because the door code happens to be the same. Inside, he ends up witnessing the “union” of his department's teaching assistant Yoon Doa and his classmate Hong Ijae. The shocking scene passes along with the night, and the next day, Yeonsu belatedly realizes the gravity of what he did.