Just curious if anyone knows... When I looked up this mangaka on Baka-Updates, it listed them as female, and the website profile I found also lists them as female, so I'm going with that. But this page of Wife and Wife implies that Minamoto-san is a man. Mistranslation, ambiguous original phrasing, or did the mangaka's gender change in the meanwhile?
I can't figure out what's going on with the gender thing, actually. Minamoto Hisanari seems to consistently list themselves as female on all their online profiles (their Pixiv profile also says female) but yeah, they refer to themselves as a man in Wife and Wife, there's what Erica Friedman said, and the portrayal of "yuri marriage" in The World is Full of Yuri was done in a way that was... not something I can easily imagine a woman who was attracted to women writing.
Whatever the case, definitely one of my favorite yuri mangaka. That small criticism of The World is Full of Yuri aside, their manga is so sweet and good-natured it's outright poignant, and I can't think of anyone who does that type of yuri better than them.
Minamoto herself says she's a woman. What's going on the "afterword man" is just that the Japanese sometimes use "man" as a suffix to mean someone doing a thing. Women do it too. The incongruity can be part of what tickles them about it.