I’m confused about this seal thing? If it’s so important that it could be used as MC s...

If we follow manhwa logic here, country police will likely let it slide by the reason of being "his father" and they are "family"

That’s not manhwa logic that’s literally how things go on in Korea lol

So in Korea seals can be used instead of signatures? What happens if somebody lose their seal? Do they get replaced and lost seal cancelled or sth like credit cards?

Dunno in korea. But in japan, seals or hanko is actually more acceptable than signature, you can report it to cancel the seal and get a new one.

Ahh thank you!!