Cum on your belly [Ending C2]

You can't cum on her, and you can't risk moving your hand to pull up your pants, so you need to roll onto your back so the cum goes onto your belly instead.

You try to shift but you're truly stuck between a wall and a hard arse. You can't shift to the side, so you try to thrust up and free, but all this does is cause the searing pleasure-train to speed up and as your penis head pushes up through the valley of her tight pass, slipping smoothly on your pre-cum it's enough to send the spunk-express over the edge.

There's no avoiding this disaster so you keep thrusting between her naked butt cheeks until you're firing your warm man-milk into her anal crevice, filling butt valley with a creamy river of spunk as your cock head tingles with delight.

Seconds later her moans crescendo as she comes too - either from her sensitive stimulated anus or her thighs pressing against her clit.

After her orgasm subsides she flops onto her front finally giving you room to move and un-trap your dead arms.

You let out a long slow breath, savouring the tingling of your twitching bell-end.

That felt unbelievable! Cumming all over your girlfriend's sister's butt! Of course you would have preferred to cum in her arse, but still that was some experience. You feel satiated and want to drift off to sleep, but... you can't leave her with an arse crack full of your spunk, that would lead to difficult questions for sure.