
He's confirmed to be 19 and Changdeok is 25, the older one is not accepting any of his advances and does not see him that way at all, the author is also not sexualizing Jongwoo (not even a proper shirtless panel, let alone anything suggestive) in any way. The current year is 2019 so there'll most probably be a 5-6 year timeskip soon.
I understand if the age gap troubles you but I don't think the author is fetisizing it, these kinds of big albeit legal age gap relationships happen all the time everywhere so the author maybe wanted to explore the complications of handling this kind of story and relationship. This also adds more angst and conflict for the characters, and a good excuse for slowburn.
There's a way decent way of handling these kinds of themes, some manhwas feel very predatory but this author is doing it a proper way imo.

It's not exactly a 'knew you since you were a kid trope' is it, he met Jongwoo at 19, even if I don't want anything to happen right now it's true that he's an adult (atleast according to my country). The trope you mentioned makes it sound like Changdeok met him way younger and makes the situation sound gross and illegal tbh.
You don't have to try to be open minded, if you don't like something don't read it. No need to go against your boundaries over a BL lol

9TEEN is definitely still a kid. If he were, say, 21 or older, I could get on board but let’s be real, age gaps don’t need to dip into the ‘barely legal’ zone. The fact that we even need to have this conversation is already a red flag. Like… if you have to time-skip just so the characters can share a kiss without it being questionable? That’s kinda telling, lol.
Take Dangerous Convenience Store now that’s how you do it. The age gap there is something like 25 and 45, and it works. It feels mature, not messy. But hey, I get that people have different views on what’s acceptable when it comes to age gaps still, there’s a line between preference and problematic.

Red flag? Just be upfront and call me what you're wanting to lol. Are you saying all these people who are enjoying this manhwa and the author themselves are all problematic?
I don't why you're taking both of our replies so aggressively, we both said you don't have force yourself to read something and that I get it that it's not for everyone.
My brain won’t allow me to read this because the age gap is concerning me. Why not just make him a homeless man like why does everything need an age gap ughh He’s a child Jesus Christ