The Cleaner

One day, Jin Yisu is ambushed by unknown assailants and loses his father, the only family he had. As time passes, he begins to realize that his father did not belong to the ordinary world.
When the assailants strike again and Jin’s life hangs in the balance, a group claiming to be his father’s former colleagues appears. Through them, Jin learns the identity of the attackers: the 'Cheongdo' Group.
Cheongdo seeks to mobilize its operatives to illegally expand and redevelop corporate-run city districts, ultimately securing a political foothold. Upon discovering that his father and those former colleagues were covert agents resisting Cheongdo’s system and violence, Jin Yisu chooses to join their ranks.

Original Webtoon:
Naver Webtoon, Naver Series