Oh! Pilseung Kim Gwajang

Kim Moojin's job was to support the supernatural beings known as "vagrants" on missions, cleaning up the messes they leave behind. Then one day, he is killed in a fight between vagrants, but to his surprise, he wakes up in the year 2002, the peak of his youth! Though excited to relive the good years, he finds out that, unfortunately, he's been cursed by a demon! Now, the only way for Moojin to cure himself is by working with the ones he hoped to avoid the most... the vagrants.

(Source: Tapas)