What does the finale of Korean drama mean?

Jing Jun, who had to leave, and Dolan, who had to let go, were happy for fear that they might forget their love. At this time, Yunzai's condition in the hospital suddenly deteriorated.

Introduction:

It's about a boy 18 years old who suddenly becomes a 30-year-old man one day.

Xu Yun, a 30-year-old doctor, is possessed by the soul of a high school ginger (played by Shen Yuanhao) who is only 18 years old. An accidental soul exchange, after asking around, Xu Yun came to the hospital where Jiang was in a coma, only to find that his photo appeared on the poster of the hospital. It turns out that this hospital is the place where Xu Yun used to work. Xu Yunzai's fiancee Guidolan (Li Minting) also suffered an unprecedented experience because of her fiance's sudden change?

Extended data:

Introduction of main roles:

Xu Runcai:

Actor? Gong Yoo

At the age of 30, Guidolan's fiance, pediatrician, mature man with handsome appearance and prominent family background is definitely the groom's first choice. The wedding day is coming, but I don't know why I don't care about the wedding preparations, which hurts Dolan.

Jiang Dao:

Actor? Won-ho Shin

18 years old, pretending to be an adult, cynical and willful. In a word, when he was 18 years old, he was still a teenager at the end of his youth. An accident of fate left his body in a coma in the hospital, but his soul existed in Xu Runcai.