Spoiler
The reason why Junseo is well loved and expected to be the end game is because he is the most well developed, with the most screen time and has the most chemistry with the main character. Instead, the main character ended up with someone with little development, on top of rushed romantic development. It's ironic that even the ending has more focus on Junseo getting rejected, while the romance between the "main" couple feels like an afterthought.
In any case, I believe the title Unripened Expression refers to Junseo, and that would actually make him the true main character of the story. However, this message is lost because the author decided to make this a pseudo harem where the boy with the most focus losing. The rushed ending and the lack of any side story made this a very unsatisfying read. It's a shame because it was genuinely fun and enjoyable for most of its run. It used to have a 9.5 high score, and the ending single handedly sinks it to 8.7, the biggest drop that I have ever seen in any webtoon here.
Oh so Junseo guy is not the endgame? Haven't read it yet but if everyone likes Junseo then I'll surely like him too. Well not reading it now