A young psychiatrist name Jung Byung Hee enjoys helping many patients, and starts a new life by making weekly visits to homes in need of help for free. One day, he gets a call from a woman, stating that a young lady by the name of Lee Yejin is suffering with a mental disorder called Posttraumatic Stress Disorder (PTSD). This disorder causes Yejin to fear people, because of past experiences.  Byung Hee promises that

It is autum. The leaves are changing colors, the days and shortening, the nights are getting longer, and the cool air is blowing.

Yongguk, Zelo, and their interesting but tragic love begins when they first meet in high school....