Maybe

Ava watched as her sister finished watching the video, smiling as she left the room. She sat back on the dog bed, jumping slightly in her place, bobbing up and down and rubbing her crotch in desperation. Shortly after, Jane returned with a glass of orange juice completely filled to the brim of hers, a wicked smile on her face.

"Here's your breakfast" she said as she knelt down, putting the glass down to remove the gag.

The moment the gag was out of her mouth, Ava gasped before speaking, desperation in her voice.

"Please, Jane, let me piss! I don't care if you have to masturbate me! I can't take it anymore!"

Jane watched her in amusement before grabbing the glass and holding it out to Ava.

"If you drink to the last drop, maybe I'll let you piss."

Ava dubiously stared at the glass, afraid her sister was lying, but what other choice did she have? She took the glass and began to drink slowly, for her bladder was throbbing strongly when she felt the liquid running down her throat. After a minute and a half, she managed to finish it, handing the glass back to a smiling Jane.

"I'm proud of you. When I let you go, go to the bathroom and stand in the shower with your legs spread and wait for me" she said as she got up and went to her nightstand to get a small key.

With it, she unlocked the handcuffs and allowed Ava to go to the bathroom, unable to look her sister in the face of her. As she stood up, the pressure on her bladder seemed to worsen, and she had to **** herself to press her hands into her pussy and move her legs as close together as possible. It was hard to believe that even if it was biologically impossible for her body to urinate without being given an orgasm, she would continue to act like it wasn't, forcing Ava to do the same rituals she did in the past to cope with her urge to piss.

Stepping into the bathroom, she looked longingly at the toilet, remembering that she didn't need to do number two now, and that only meant one thing, whatever her body ingested, be it liquids or solid food, would only increase her urge to piss. She opened the glass partition and stood in the center of the shower, her face facing the door, and, with some hesitation, spread her legs wide.

Immediately, the pressure on her bladder increased, if that was possible. Ava moaned as she squeezed her pussy with all her might, her fingers clenched into her urethra, feeling the moisture escaping from her vagina. Taking a deep breath, she spread her hands, suspecting that her sister would prefer her that way, and she wanted every opportunity to piss. Jane entered at last, her hands behind her back and smiling enormously.

"Sorry for taking so long, I had to prepare a few things before we left."

Despite the implication that they were going out, and most likely had to go naked, she decided to shut up, trying to please her sister and allow her to let her piss the hell out of it. Jane approached with a smile, admiring her sister's naked body.

"Close your eyes and don't open them in any context or I won't let you piss" she said in a threatening tone, but her smile didn't leave her.

Ava closed her eyes just as she asked and waited. It didn't take long to hear her sister step into her shower and kneel in front of her, running a finger over her pussy, making her shiver. Jane pinched Ava's clit, causing her to moan with pleasure, before descending into her urethra, causing the girl to shiver even more and bite her tongue so as not to yell at her to let her urinate immediately. She had to be her best if she wanted her sister to take the pressure off her bladder.