Pretty interesting premise! The lede is a little buried in the subtitle, but I'm not really sure how to fix that without making the title about as long as this sentence, which would be less than ideal.
Write out conversations! The story contains a lot of descriptions of conversations, but it's much more enjoyable to read the actual words being spoken. That allows you to give your characters real, well, character. Little nuances in their behaviours can really make them come alive. Right now they don't even have names. (That's actually fine in a short story like this, but in a longer story it wouldn't be.)
I was a little taken aback when it ended at chapter 5. You say this is only a short non-branching story, but I think you could do a lot more with it. (If you wanted to, of course!) The protagonist could be into his girlfriend being abused by every villain in the city. She could be secretly into it, which explains why she keeps losing. The 3 ordinary criminals could ignore him when they gangbang his girlfriend, because they've already shown they can beat a superhero, so he wouldn't be a threat. The protagonist and his girlfriend make up at the end of the story, but you could add a branch where they don't. The protagonist is just an ordinary dude right now, why not let the experience turn him into a bad guy, either super or ordinary? He could turn Wonder Whore into an actual whore, too. Or maybe go the complete opposide direction, get her some proper training to stop her losing all the time (or try, at least). "She was just lying there passed out" is another point where the protagonist could really take things in a very different direction. The possibilities are endless!
