It's unclear if he's bisexual, but he is attracted to women as he likes Naoto as well as finding Yukiko and Chie attractive. He doesn't find Rise attractive whatsoever though. Golden ramped up the ambiguity on whether he is attracted to men.
People need to stop with Troy Baker's outdated interpretation when he recorded Kanji the first time around. It might have made sense when the game first came out, but Atlus has confirmed he is not gay since then. That and he's just recording a dub of a translated script and can't be considered word of god.
No nothing is confirmed its up to you to decide, being a bi is the middle ground so to speak to avoid discutions.
I mean gay as in being 100% attracted to men and not women, which Kanji isn't and the games clearly show this. I'm not saying he can't be attracted to men (and I honestly think he is on some level) and that is where the interpretation lies.