I've never been to Osaka (other than the train stations and KIX and Itami airports), but I lived in Tokyo for the better part of my life. Hate to break this to you, but Japan is very homophobic. As one of my Japanese friends told some of my gay and lesbian friends, "there are no gay people in Japan." Uh, yeah, right. And I was standing near this exchange too.
Anyway, I'm sure there are some districts in Osaka that have gay establishments. Others may know more about where to go in Osaka. Hope this helps.