Melancholia

Ji Yoon-soo, math teacher, set to marry, assigned to prestigious Asung High School in Gangnam.

Yoon-Soo realizes that Seung-Yu is the one who guessed the math club's Calculus question.

When Yerin learns that Seung-yu used to be a math prodigy, she feels uneasy.

Seung-Yu and Yerin start preparing for the Math Olympics in earnest.

Seung-Yu opens up to Yoon-Soo about a past trauma she hasn't been able to tell anyone about.

Yoon-soo has mixed feelings about Seung-yoo's confession.

Four years later, Seung-yu has become a renowned mathematician.

Finally reunited with Yoon-Soo, Seung-Yu hovers by her side and tries to get closer.

Seung-yu tries to get Yoon-soo to come out of his shell, just like he did for her.

For the first time, Yoon-soo opens up to Seung-yu about her pain and hurt.

Thanks to Seung-yu, Yoon-soo finds a little bit of laughter, and the two share a special moment.

Seung-yu said that he was the subject of the Asung High School scandal and that it was a frame-up.

He is frustrated that his love may be an obstacle to proving Yoon-soo's innocence.

Eventually, they realize that Sian has been victimized by corruption in the school.

The secrets of Aseong High School and Noh Jung-ah are finally revealed to the world.