
You know even if he didn't agreed exactly just when you think about it he knows Hwi loves him since he asked him to go in a date but rather than give him a specific answer he just sleep with him when he wants to and then go sleep with another man and what he didn't think he did a mistake? Then it's normal for him to just sleep with two people at the same period and it's doesn't matter if he hurts other's feelings just wtf is this

Yes this is why I said its a case of wanting your cake and eating it too. He's playing both sides and enjoying himself. Maybe in his mind, he wants to try it out with both guys before settling with one, but from the readers pov, its a scummy thing to do since Hwi has been showing his feelings for hm for a while now and Param has been kind of brushing it off :(
Ok so latest chapter spoilers -
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They have sex unfortunately. Mr Han is surprisingly not a douche about it and asks for Param's consent and they do it. Then he takes a shower and Param leaves. He says they have work the next day blah blah and runs off. And while he's on his way back, he wonders if he made a mistake and shit. Basically he says it cant really be a mistake since he wasn't drunk and he was in his right mind and wanted it and he's always been attracted to Mr Han anyway.
Also on another note, although I think Hwi asked him out I don't think Param really agreed so I don't think it could be considered cheating, just Param wanting to have his cake and eat it too.