Jega Boiseyo?

Do-Hwa, who can see ghosts, becomes susceptible to possession starting on her 30th birthday. Coincidentally, he is possessed by a lustful ghost who happens to be a virgin. Wandering in his possessed state, he encounters Mu-Yeong and tries to attack him. However, Mu-Yeong, being a grim reaper, recognizes Do-Hwa's possessed state and helps the lustful ghost achieve enlightenment...

(Source: Bomtoon, translated)