It really depends on how they write it. To properly handle the mental health themes there are 4 steps. You need to show the descent into madness(I think we finished this part), rock bottom(what I think is coming next chapter), the (internal) desire rebuild and the actual rebuild.
The problem is right now is the fact that is a romance. So the internal desire cannot be motivated by another person. The other person can be the spark but not the cause. Plus as of now Nanjo is done with him, so you need a reason for him to change his mind that isn't contrived.
Most yaoi authors tend to cheap out by having one of the two get seriously hurt. Which I think might be happening with the car accident. But this story is a little to real for that method to be effective.
Again we will see. They have been a pretty good writer thus far.
"So the internal desire cannot be motivated by another person. The other person can be the spark but not the cause." Hmm interesting
i don't think Nanjo would accept the current behavior of Mokyeon, maybe he will be the spark as you say, by having a real talk with Mokyeon like yes i kissed you back because i also had some feelings because you are actually a lovely person, but like this we cannot be together: get your shit together, stand up and walk straight in your boots, be deserving of me and then come back to me, we'll see maybe i'll accept you then

This might be controversial but I think it needs to be said. This is a very good(uncomfortably so) depiction of mental health issues, unstable relationship, alcoholism, self harm and suicide. I actually think this author is amazing.
The problem is right now this is a huge genre shift from a traditional toxic yaoi. The cover indicates these two are supposed to get together. As frustrating as Jinx, killing stalking, and other yaois like it are most of the narratives are clearly a fantasy (rape fantasy, but fantasy nonetheless).
So depending on how the second season turns out the author unintentionally false advertised. Either they get together at the end in which all these themes may have been handle really poorly depending on how they write it or it was always a character assessment and the yaoi was use to lure the audience in.
I hope they can write well enough for it to work but I can see the signs that it might not pay off. We will see.