"The main plot is structured around the special relationship between a trans woman and a 
femboy."
Why.... is it always a femboy 
		 
		
	 
Cuz its hot? Maybe some of us enjoy the juxtaposition of a feminine body with an "extra attachment" but do not enjoy the sight of a typical dude getting bent over and railed. It's not cute or hot. Its just pathetic(in my opinion).
If it has to be a male in such a position then this at worst is an acceptable compromise and at best actually ends up being a double. Also that doesnt look like any transwoman I have ever seen and I look at those kinds of lewds a lot so even that is a stretch in my opinion but thats what fantasy is for.
Maybe if it's "always a femboy" in this position that should tell you something about the general consensus. Or maybe it's confirmation bias on your part. Who can say? There is never enough niche content for those who seek it.
I hope you eventually find more of what you are looking for, but allow the rest of us to enjoy what we have found. 
- Take my comically frank response to a meme question as amusement.  
