The police officer in this series is doing his job and has a boyfriend to come home to, he seems secure in himself. The police officer in Killing stalking was a not following orders and could be seen as harassing members of the public (or stalking just to keep it fitting of the title) which is why he was moved from his original position and it appears he got sacked or is going to face disciplinary action at his current job (where he ended up kidnapping and battering Sang-woo).
The police officer in this series shaves his beard to feel better about himself and impress his boyfriend, the police officer in the other series improves his appearance so he can try and stalk Sang-woo.
I know but there is a possibility that the vampire and the demon here would get caught by the policy Officer just like sangwoo and bum
A bit of nostalgic in the detective’s part in Killing Stalking. That annoying police officer who kept butting in business like this guy here.