I actually have no idea
Every time I draw something like this I feel like I need to apologise
"Ah!" Dean arched forward and squirmed aimlessly in Castiel’s lap, weak grip on his arm doing nothing to stop the pulling and stroking on his tail. He didn’t want to look but his black eyes had nothing to look at except the assault being done to his tail. And it just felt sooo good.
The angel smirked and tightened his grip on Dean’s tail, feeling the hunter’s body tremble, preferably his legs which knocked against his thighs. He dipped his head forward and kissed the bite mark on Dean’s neck that he made not a moment too long ago. He latched onto it and sucked, caressing the center of the spear-like tail. His other hand ghosted around the base and he gently pulled down Dean’s jeans to get to it. Dean was too focused on the lips on his neck and the stroking on his tail he didn’t register the other hand going for the base, moaning and grunting and panting pathetically, pressing his back against Cas’s torso and not thinking of getting away. Heck, he couldn’t think at all with all this going on!
"A-AH!! Nnngh-ah! C-Cas-NO!" He straightened his back and a cold shiver ran down his spine from the sensation. He took a moment to actually feel the hand at the base of his bottom rub and squeeze sharply. It kinda tickled now that he thought about it and the tingling spread throughout his butt and his spine, producing a small chorus of giggles and moans. Dean wiggled forward to get away but Castiel slammed his legs on his own, thighs squeezing hips and circling those legs around his to keep him pinned.
"Ah ah ah~" Castiel sang teasingly, "I’m not done with you yet, Dean. I believe you owe me for all those times you have tortured me with my wings so this is your payment and a way to ‘get even’ with you."
Dean cannot argue with that and he can’t find the words to argue with because he his mind is a mess and he just can’t resist those skillful hands rubbing him the right way. It was only a matter of time before he thought up a plan to get back at his angel and-
"Ah!" He bucked and blushed furiously, head dropped low and eyes gone wide in recognition. No no no…
"Dean… did you just come?"
Here, hold my love