From what I have seen, and from the people I have met and spoken to who are gay in Japan (both foreigners and Japanese), things seem to be much better here that in some other countries.
On tv, you can see transgender, homosexual, and men in drag hosting shows, being guests, doing commercials and so on. Thanks to manga, anime and other outlets, youth culture is indeed exposed to same sex relationships and don't seem to have much of an issue with it.
Heck, when my wife and I were shopping for wedding rings, the staff member who was showing us the rings was very openly gay. To the point that he was telling my wife how handsome I was, how lucky she was and how his heart beat so quickly in my presence. At the time I had no idea what he was saying as I was still just getting started with learning Japanese. So I just smiled and laughed when he laughed and found out what had been said over lunch. Haha.
The Japanese culture has changed quite a lot in the past few decades as more and more people choose not to start a family or even have children due to work, disinterest and other factors. This kind of situation seems to work in the favor of openly or even secretly gay couples as the pressure or expectations to have children appears to be decreasing.
I'm sure if you did some research or looked around you could find a gay community in Japan to ask more questions.