At first, yes, Sul always feels nervous and anothers, given her overanalyze personality. Sul herself is in the wrong too. In a relationship, she should trust her partner, if she can't then talk about the problem and search the solution together.
But thankfully, as the story progressing, she learns to trust Jung and there's a chapter when she's beginning to think her relationship with Jung more deeply. Their relatioinship is better now (I'm still in season 2).

I don't know why this story have to involve In Ho till now. I will very dissapointed if the author decide to make it Sul x In Ho in the end. I mean, I have always seen Jung x Sul from the beginning, and I already developed feeling for them. In my opinion, Jung is nice in any ways though he has mysterious aura and (well, I admit) shady/sneaky, but still he's been so nice to Sul. I can't if they decide to break up, my feels 🙁 🤢

(but I worry too for Sul safety, you know.. what if she make a grave mistake toward Jung, considering Jung isn't really forgiving. Well, hope with Sul inteligent, she can avoid it somehow 😐 )

Edit :
Ok, I have read till the latest english chapter (mid season 3). Their relationship are progressing, though I know Sul is at the point scared of Jung, just sometimes. And Jung is ughh I don't know.. but he uses manipulative ways for Sul safety, you know there's a chapter that Jung will do with his ways (I can't really blame both characters for being like this T.T ). I hope I'm wrong, but Jung is becoming more possesive(??)
Nevertheless, I still ship JungxSul

I think Sul is going to end up with Jung. From the very beginning, the story was about them.

When Sul and Jung are not arguing over some weird thing, they get along really well. They share interest, some ways of acting... She is the one that treats Jung as he deserves. He tried his best to get near her, always trying to help. Yes, his ways are weird and when he has a problem is not direct like she is, but isnt it a lot weirder how In Ho is always beating or talking about punching people and just because Jung did it once he is in the wrong?
It would be a little unfair if she ends with In Ho: Jung suffer believing Baek siblings have stolen his fathers love and money, and now Sul, his girlfriend.

Sul never thought of In Ho in a romantic way, in the later chapters it seems she thinks he might love her, but it is not implied later in the story but to show that she cares for him as family member... Not like love: She is developing things for Jung.
In Ho, surprise of how hardworking, naive and nice Sul is, cares deeply for her: If Jung wasnt her boyfriend, she would fall for In Ho. She also is always trying to help him and is so hard working that he is surprise and in a really good way. They would be a really good couple.

She started having these feelings for him knowing that he is different and accepting him; but that cold look...

When the story behind In Ho`s hand is uncovered, they might split... But I think and hope they will get through that. Either couple is cool.

Definitely In Ho! They just get along so well! Plus the latest chapters (translated) show there's sooooorta a possibility they'll be a thing? I ain't getting my hopes up... but if the author decides to make him the main dude, it'll be a relief.

Honestly.. Yoo Jung freaks me out.. He's malicious, but in a sneaky way. He has an even bigger victim mentality than In Ho (although in the latest chapters I'm starting to think In Ho is justified in thinking so), swatting anyone who gets in his way, regardless of what they do (like Sul herself at the start as we later find out). I mean it was heartbreaking when he split up the 'honey' guy and the assistent dude just because they accidently revealed what Sul should have known anyway. Heck, even Suls bro was like 'sumin's off 'bout him, kinda creeps me out!' And went on about how he felt comfy with In Ho B]

Anyways, for me it's either In Ho or no one.
..
Well....... Bora seems chill too 😎 Ahem but she's got the other guy (WHO ROCKS)
So In Ho it is!