
Well, i don't think it's that easy to find someone with just an address. Isn't only the name of the road and town written in the id? I doubt you can go around asking neighbours if they know where someone lives because there are a lot of apartments in Korea and even neighbours might not know you.
As for the rest, well i agree with your last comment lol. There's no way i can think that far.

Continuing because for some reason it got posted , so if Heejae knows where he works he could have just followed him from the office till where he lives. But since Seyoung already knows how Heejae looked prolly would have given him an alarm if Heejae had taken the appointment or even as a delivery man in fact would have given away because "HEEJAE IS HANDSOME" should have just asked Oh la la for the stalking matter
I got a big ass qs and ie, didn't the id Yoona showed had the address written over there? Am I dumb? He could have just asked for the id from her and then go to soc med and stalk him. Socmed stalking is so common anyways? And as for the counselling, he could have just gone ahead with the appointment, he is rich anyways bruh or he could have just acted as a delivery man after stalking Seyoung for a few days and understanding his daily life pattern, this way he would know things- dude I'm fucked