Dat ass

What makes you think it's flat and featureless?

I would zoom into the lack of ass she has in the picture, but the resolution is shit enough as is.
Just take my word on this one, trust me.

is this you OP or some gf?

Can you describe how you know? How can you tell the difference between a flat and non-flat ass?

And what does "featureless" even mean?

Don't ask so many questions.

Here's a non-flat, non-featureless ass.
I'd post a picture of the opposite, but you wont get a better example than the OP.

Hnnnng.

...

No. I'm not into trannies

I quit the 2D game, user. I have no tolerance for such feels.