People make mistakes and go back on their words all the time. It's called being human.
That doesn’t mean it isn’t shitty and that he isn’t a hypocrite.
At the time he was sincere and it literally just happened. He'll only be a hypocrite if it happens again and he doesn't own up to it.
And people are also allowed to change their minds without being called names.
You’re only a hypocrite if you do something more than once?
Everyone can make one mistake. When he said he wouldn't fuck both of them, he truly meant it. He made a mistake (or not), it happens. Hwi's not even his boyfriend, it's not like he cheated.
He didn’t make a mistake. Param wanted to sleep with Mr. Han and he did. It wasn’t cheating but it’s cruel to accept a date from someone who likes you, then turn around and sleep with someone else the next day.
He's clearly regretting it though. So he made a mistake. And it's not cruel to have sex with different people when you're single. Param is single even if Hwi likes him so he could do what he wants.
And for everyone saying he’s allowed to mess with both- Param literally said a few chapters ago he wouldn’t. Jun suggested Param date both and he flat out refused saying he wasn’t like her. I guess he’s a hypocrite now (￣ε(#￣)Σ