Shocked no one has mentioned Oyasumi Punpun yet. It's been quite a while since I read it but it did resonate with me quite a bit. It always felt like Punpun was alone even when he hung out with his friends and other people. Mainly because he's struggling to figure out how to even be a person and he doesn't have much guidance on that.
By the time he meets Aiko again when he's older, it's cathartic for both him and the reader to realize that she isn't living the great life he thought she was living. They were both from messy, dysfunctional families and that kind of upbringing really messed up their ability to make meaningful connections and figure out what the hell they're supposed to do with their lives.
There's this concept of having a gaydar in the LGBT community and I think the same applies to kids with trauma, they just attract each other like magnets without even knowing lol. That's how all my friendships played out, and that's why Punpun got so hung up on Aiko despite them growing distant.
I read this series the same way i approach other works of fiction that tackle depression; I expected it to give me some sort of answer, like what the hell I'm supposed to do to pull myself out of this rut I'm in. It didn't give me one. I'm glad it didn't since it makes me feel a little less alone. If the answer was easy, I would've figured it out by now right?