Raw first impression (haven't read the thread)
INCLUDES SPOILERS
I like that there's music AND that it isn't generic AVN/Ren'Py/RPGM music. Even better, some sound effects!
Art is a cool style. Nicely done and well suited to this variety of parody work. The faces are at least as good as professional comic books (granted, some comic artists are better than others).
IMHO, the word "titty" is too playful/fun/cute for this kind of a scene. This version gets right into the nasty very quickly, and just as the action starts, I found myself giggling at it. Saying "breast" may seam hoity-toity or overly polite at first, but I honestly think it fits the tone better. Even plain old "tit" would be better than "titty."
The first appearance of Mutant Sigma's face was off-putting. It vaguely reminds of a certain real-life person who is the LAST human being I want to be thinking about while trying to enjoy this type of material.
The tailbone fracture is a bit too much for me. As far as violence in porn goes, that's just personal preference, I suppose. I'm definitely not into gore, which (even without visuals or blood) is how I would categorize that. More importantly, the fact that she's JUST suffered that level of injury and is still able to calmly speak and express concern about what the monster is doing in regards to sexual positions breaks through my willing suspension of disbelief, and I've got a pretty high level of tolerance for lack of realism (especially when the context is already sci-fi). Bone injuries are a not uncommon part of real life, and they are extremely painful, even just a fracture rather than a full break I think would be far too much for her to still be acting that calmly, or frankly even give a crap that she's being fucked, especially with him positioning her so that that tailbone fracture is being pressed on directly with every thrust. She would most likely just be crying and screaming in pain at that point. If it seems like I'm putting way too much thought into this, that's exactly my point. I don't want to be distracted by thinking about that sort of thing while playing this kind of game or reading this kind of story. It's immediately followed by an ahegao, which I love, but again the reference to her being dropped on her butt only served to remind me how intensely painful that would be for her right after getting it fractured.
Even if it's short and simple, the animation plays smoothly and looks good. Don't forget to add animation to the game's list of tags. It's a big seller for a lot of people, and this one is done pretty well. I like that her hair moves during it, that's a nice attention to detail for hand-drawn art.
There's a few typo/grammar hits to double check, but it's not terrible in that regard. The writing is generally pretty good.
Overall, I like it a lot, enough so that I wish there was more to it. It's a little jarring to be so succinctly JUST the sex scenes, like watching a video of short collected clips instead of a whole story. It makes me wish there was more to it. Looking forward to where you go with this.