Murimbingui

Seung-Won, who lost his memories in a car accident, possesses the body of Chu Sa-Hyeok, a supporting character in the novel "Jegal Unhwi". As soon as he opens his eyes, Seung-Won was having an affair with Ha Ji-Kwang, despite being completely oblivious to it and is under the impression that he is dreaming as he's on the verge of death. Somehow, he is unable to wake up from his dream and continues to live on as Chu Sa-Hyeok.

(Source: BOMTOON, translated)