i think its quite the opposite actually, its when hes indulging with mitani that it feels superficial and fake, because it is only then that he solidifies himself in the role of a man, when that is clearly not the best label for him. over and over again, there are instances where he feels like hes not "man" enough or that hes lost his pride as a man, that hes a failed man, etc etc, and theres an emphasis on him turning or becoming a true "man" once he has sex with a woman (mitani). even kei pointed this out like last chapter or maybe the one before that, i cant remember, saying hes a true man because he had sex with mitani. but when hes with kei, neither have to fit within one construct or the other and allowed to exist as their true selves, essentially free of the ideas of man and woman. they revert to the times before they had to grow into one or the other and theyre just themselves.