I know this comment is from two years ago but I still want to respond (≧∀≦)
I'm only on chapter 6.2, but to me, Jongyi's character feels very neurodivergent-coded. Taking things literally, speaking his mind without filter, indifference to what most people like, feeling like an alien, not wanting to talk, getting excited over certain foods (milk), bad at social cues, zoning out, flat affect, doing "odd" things that aren't age appropriate... all those things could be read as childish or airheaded, but personally I relate to him a lot. Things could change, but that's how I read him right now.

I haven't finished this one yet, but I personally find characters who are so floaty and childlike really unappealing. Beyond his appearance, he acts like a 5-year-old, which is just...incredibly unattractive. But clearly, neither of the protagonists feel the same way. And on that note, they are both ridiculously shallow, although they like to act like they're morally superior to the partners they broke up with in pursuit of this empty-headed pretty boy. We'll have to see how my opinion changes by the time I finish this.
Edit: Dropped it, so I guess I'll never know what direction it took.