Why does this joohoon dude reminds me of gintoki? a twisted harada gintoki to boot lol

I see how you get that. It's that silver natural perm and those dead fish eyes. xD
(Looks aside, he's too much of an uncool asshole to be anything like Gintoki, tbh... )

A lot of manhwa artists seem to get their character designs from anime/manga so it's not a surprise to see similar characters in looks and mannerisms.