Basing it from when this was released and it's in japan, maybe he did saw gay couple, but was too bitter from his past love life trauma to accept it. Also, he's daily life, he hangs out at the bar, he does hook ups, so it's hardly he'll see happy gay couples.
I did like this one, but after rereading it, maybe some are unrealistic, and the fact that I am not a fan of ukes/semes sleeping around left and right, I just skipped those parts. It also gave me a new perspective since I read this when I was like 18, and now I'm in my mid-20s. I still like it, though. Since I don't really care much about realistic stuff. The reason why I read anyway is to avoid reality, lol.
The sequel of this manga is so much better imo, maybe because it's more newer. And it still continues Misaki's doubts in gay love, which is consistent. And I love how Mikado's there to erase those doubts slowly. They became a cuter couple in the sequel.
I think we can all agree that Misaki's inner monologue about his sexuality was one of the only things good in this manga. I don't like the trope of "this guy was a cheater so I am going to just end up sleeping with whoever and wherever now" trope. It happens in real life, yes. But it seems a little bit TOO common in BL in general. It misrepresents queer people to be folks who only care about sex predominantly. It's also weird how Mikado falls in love with his bully superior. He kept on shitting all over him and he falls in love with him? Bitch what.
Also, to each to their own and everyone has their own preferences, but this is far from the "best bl". Misaki gets sexually assaulted left and right and for what? What purpose did that rape scene fulfill? Absolutely nothing. This manga would have been the same without that rape scene. "All gay people do is have sex", DID MISAKI NEVER MEET A GAY COUPLE??? Why do people think gay people have been FIGHTING to be able to get married??? Please, there is a limit to being ignorant no way ya'll are calling this "realistic".