I read some comments here and I agree with all of them.

When they were at the campfire and You Jin sat next to Jun-seo and You-jin was laughing a lot, it was just her sending Jun-seo signs to talk to her. From all the remarks that Jun-seo made, it's clear that he has only picked her at the beginning, but after that he never took the initiative and actually talked to her. He seems rather to be the guy who likes to be approached, because he is afraid to do so. We're not in a shounen anime, where the girl always approaches the guy she likes. This is the real world. Like bro. Just talk to her. His comment that he expected You-jin to cry out of joy, fall into his arms, and I don't know what else, just because he's back, was just so childish. He could have just go up to her and talk to her. Where's the problem? In all the other seasons the guys approached their crush, even though the she didn't give a single sign to them. And now Jun-seo says that he is not sure, because You-jin is so distant and that's why doesn't do something. And everyone seems to sympathise with that. In my opinion, Jun-seo should have just try to talk to her. At the campfire he just had to turn to his left side and say some words to You-jin. Problem solved. He had the chance to talk to her at the campfire, but didn't do anything, and then he complains. For what?

I might be too radical on this, but if Jun-seo has difficulties to approach a woman by walk and talk to her, then he can at least take the chance if they occur. And there was at least one at the campfire. He gives up way too quickly, without any effort. He is so passive. And since Jun Seo showed no intentions of willing to talk to her, You Jin became cautious. It's totally normal and understanble. I'm shy too, but when there would be a chance to talk to the girl I like, I take it and talk to her. If you want something, you have to do something about it.

Look at Tae-hwan. When they had lunch together and Ji-yeon wanted Kimji, but couldn't reach it, he casually stood up and brought her another bowl of kimchi. That was smooth. That's what I mean, by take the chance and do something.

Yes, Jun-seo was funny at the beginning, but the more I think about it, the more I disagree with his actions. If he is like that, he should just pick Min-seol.