Sorry to be boring, but I think it was the
Streets of Rage whip girls for me, too
I remember facing Electra in SOR2 for the first time. She's singing in a bar when you first encounter her. It looked like some kind of nightclub act, and Jessica Rabbit would have been my frame of reference for that at the time. Awoooga! Then she throws off her cape and reveals that costume - the leotard, with the fishnets and boots - and starts lashing you with an electrified whip! In hindsight, it's pretty kinky stuff for a child to be witnessing, but I think what really impressed me at the time was just the fact that you were fighting a beautiful woman. I had seen sexy female characters before, but they were usually love interests or allies to the hero, not enemies to be physically fought. So this kind of blew my mind.
SOR also allowed you to
be a sexy, kick-ass girl in the form of Blaze Fielding, but that's a whole other story...
Around this time I got pretty interested in video games with female enemies (and playable heroines too, but again, that's another story). I would sorta gawk at them in the arcades. Games like
Sunset Riders and
Golden Axe, and probably a bunch of others I'm forgetting.
Mortal Kombat was also a big deal. I may have been aware of it before
Streets of Rage, though I'm not sure if I actually played it. I don't think I even saw any of the gruesome fatalities being performed on Sonya or Kitana, but the knowledge that it
could happen to those gorgeous gals just as easily as the male characters was kind of mind-blowing in itself. I guess that's not zako, though - ryona yes, zako no.
There was other stuff that fed into my interest from an early age. I was always fascinated by any kind of action-adventure scenario featuring scantily-clad women, even if it was really silly. This is going to sound goofy af, but
Abbot and Costello Go to Mars made a big impression on me as a kid. Spoiler alert! Bud and Lou don't actually go to Mars in this movie. Instead, they go to Venus, which is populated entirely by women. There's no ryona or anything, but there were tons of beautiful, spear-toting Amazonians, and it definitely did something to me. To this day, the idea of all-female armies, or even all-female worlds, are big fantasies for me. And this movie had both!
Some years later I remember enjoying zako moments on shows like
Xena: Warrior Princess and
Hercules: The Legendary Journeys. And here's a deep cut: does anyone remember the Galafems from the Aladdin animated series? It must have been around this time that I realized this was "a thing" for me, though I'd never heard the terms "zako" or "ryona." I'm not sure I even knew what a fetish was, but I certainly had one at this point.
Eventually I went on SexyAmazons and DeviantArt and had my mind blown again, because I discovered that other people had the same weird fantasies I'd had 15-20 years earlier!