At the End of the Road

About At the End of the Road Manga:

After a car accident, Taemin finds himself in the body of Siwon, who was a victim of bullying at school. No longer a pushover, he starts standing up for himself but then meets Woojin, an old friend from the past.

Somehow, Woojin immediately picks up Tamin’s ‘scent’ from Siwon. What happened between these two in the past and how will it affect their future?