It's somewhat well-known bit of trivia about Mai Shiranui that, prior to her debut in Fatal Fury 2, her character was refined out of a rough concept described only as "ninja master," depictions of which were masculine. SNK have released concept art showing it, and the prototypical non-character even appears in the background of Mai's stage in Fatal Fury Special. But thanks to scans courtesy of Rage Quitter 87, we can see the earliest mention of this was made just a few months after Mai's debut, in the back of the manual for the consolised NeoGeo version of Fatal Fury 2. Just out of personal interest, I've done my own translation of the Japanese text, and of course I'll include SNK's inimitable official translation for comparison as well.

BONUS
Garou Densetsu 2 Human Interest Corner
—From the notebooks of NeoGeo interviewers
The Buxom Mai-chan Was a Man!?
The queen bee, curvaceous Shiranui Mai-chan, was originally planned to be a male character—"ninja master." At the time, the thought was still that "fighting games are a man's world!" But the sentiment that including a girl would be good (not without certain ulterior motives) ultimately prevailed, and so the character changed to female. Now Mai-chan is the most popular character around, and the male cast can but tremble before her sex appeal and strength that puts men to shame.
Mai-chan's Remarks:
"Ohhhh-hohoho! Fighting games, a man's world? Talk about old-fashioned. These days, girls are getting into combat sports, too. With so many weak, slovenly men around, it falls to women to pick up their slack. Oh, but being this strong, am I still fit for marriage. . . ? (The intrusive thoughts of a woman)"
And here's SNK's own translation from the English manual. Despite the reputation of "SNKglish," we are finding out more and more that these are often right on, except when a conscious decision was made to go way off.
