I won't elaborate too much because most of the other reviews have covered it.

I'll say that I agree with others that it's an overall happy ending if you pay attention to certain things, it is implied they do end up together. My issue with that is... I'm not entirely sure it had to be made a secret to the viewers. I see the "art" in making it a bit of a secret for the viewers. I get that since the couple themselves have picked to be in a relationship in secret, whether because her agency won't let her or simply to avoid the drama of openly dating, they've chosen to also make it a bit of a hidden relationship to the viewers. It's neat... but sometimes you just want to be able to enjoy the "post-story" happy moments of a relationship and we didn't get to see that.

I had major second FL syndrome, Jin Ju is adorable and I can't help but wish they had leaned into the soulmates bit and gone with that twist. I would have been content with the story being about our ML helping our FL past her demons and helping her towards a positive path in her life but them not ending up together as he reconnects with Jin Ju.

I've read some comments about there being toxicity and that really feels like a stretch. If you want a "nothing but perfect people making perfect choices" and dealing with their pasts in the absolute healthiest way possible, the dramas are out there for you. However I reserve a word like toxic for genuinely and consistently shitty relationships marred by people who abuse the love they are given and convince themselves or their partners that they've done nothing wrong or that the person deserved it. That doesn't happen here, there are choices made that hurt someone but there is reason behind it as well as genuine remorse, not followed by repeatedly making the same choices.

This is not a great review I must admit, I'm kind of throwing things at the wall and saying random things, to get back on point:
The drama had a sense of realism, with people making real if not ideal choices in certain moments, and with some good chemistry and acting. I don't think too many will watch this and feel they've wasted their time, but I also don't think it's a "must not miss" watch. It was good, it was entertaining, and although I would have liked a bit more substance at the end in terms of elaborating on the couples final standing, it was a good ending overall.