According to page two, panel five of this doujinshi (hosted on e-hantai.com) http://g.e-hentai.org/s/e95d51000b/449333-2 real XXIII's dark skinned muscular girl is called Rafaela. I know it may not be the same person, but it's hard to mistake her looks for someone else.
I still wonder what his blond_ahodge_girl is called though...
The similarity could be simply because he likes drawing dark-skinned blondes. This Rafaela looks like a one-shot h-manga character, while real_xxiii's_dark_skinned_girl is always shown having a special relationship with real_xxiii's_ahoge_girl (first depicted as lovers, then as a married couple wearing wedding bands, and occassionaly each other's jewellery).
Better wait until the artist gives some info about their names on pixiv before aliasing anything.