Both dramas are adapted by webtoons. Both Mls are young dark heroes who punish the criminals. Police is trying to catch them. Mls aslo cross the line of life and death.

A teen in both is being raised by a killer/group of killers. It affects their relationship. In Kill Bok Soon a teen doesn't know about them being a killer, In Hwayi: A monster Boy a teen knows and is being raised to be a killer too.