You have

Pinned down by her weight, you feel the large tip press against your tight ass, before pushing trying to get in. She must have lubed it, as with enough pressure her cock head slides in. It’s Huge! You moan and whimper... but pinned down as you are, you can’t move away. In fact, your squirming only helps it slide deeper and deeper into you, until you miraculously hit base.

“Ooohhh fuck you are tight. Well, you are for now, cock sleeve. By the end of our trip that’s likely to change. But let’s get you secured.”

She goes and attaches all your various straps to her self, so that as she stands you stay immobile and secured on her cock. You must look ridiculous, your small Femboy frame as the large Futa monsters cock sleeve. You don’t know if you are grateful for the black sack on your head, as you don’t have to see your shame or have anyone recognize you... but you also have no sense of direction, and are even more at the mercy of your mount. And somehow, to your immense shame, through it all your cock has never been so hard, not that you could do anything about it.

“Well that’s everything. We should start to head off...”