if you still love to lick back there
Day 6
This beauty still has a hard time keeping her hands away from her horny little pussy, so Mistress is making her keep her hands behind her head. It's still a struggle for her, especially since she's been teased so very much. Her pussy is relentlessly aching and burning and dripping. She can't take her mind off it.
But there's an extra reason Mistress is keeping her from touching her pussy while you lick her ready and waiting little asshole. She has to pee so badly. It's certainly to the point where normally she'd be crossing her legs by now. The pee pressure is so bad that she's having a bit of a time holding it, and would love to push on her peehole with her hand.
She hopes that your worship of her tender little asshole will take her mind off her full, full bladder. It does, but only for a while. It makes her hornier, which brings her attention back to her wanting little pussy. Also, her writhing in heat also stirs up her bladder, which is to the point that every move reminds her of her pee predicament. You wonder if she'll end up peeing on your head, especially since if she does, Mistress orders you to drink all the pee you can catch in your mouth, then to lick her pussy (and everywhere else) clean -- without making her cum, of course. Today she can hold it in, but just barely.
(By the way, you should have drunk another glass of water by now. If not, get it and drink it. Do not proceed until then.)