Agreed. Personally, I have no problems if they wanna explore cuckolding etc, as they're finding it thrilling/exciting; my issue is the fact that her husband doesn't know (and she wants to keep it that way, uhhhh). He's agreed to the wife swap, but I'm not sure he'd react positively to finding out she's sleeping with others now too. It's a slippery slope. This can still work out for all of them, technically, but there's gotta be complete honesty throughout the board.
Another issue is with this time limit they've set in place. At this point, I'm really not sure Soeun can go back to the vanilla lifestyle she had with her husband, which is concerning. Again, they could work something out, but being honest and open about it needs to be the priority.

They're starting with the secrets... Fuck, that doesn't bode well for the future.
Gotta say though, I really like Soeun/Jonghoon as they explore their cuckolding fetish. I'm so invested in their side of things, and honestly have no interest with the other couple. I really hope this doesn't end with them going back to their original partners. As a sub myself, finding a partner who hits all the sexual beats that resonate with you (especially when it's an alternative sexual kink/lifestyle) + you actually like/love them too is fucking fantastic.