Suddenly, you feel gas building in your bowels. Your face takes on a strained look, as you try to hold it in. The pressure gets higher and higher. Arianna is noticing. "Are you sure you're ok?" she says, the playfulness gone from her face. She's actually concerned for you. "Yeah... I'm... fine.." you manage to say. She looks worried, but says nothing and instead looks out the window.
You can't hold it in anymore and let the pressure go. Instead of hearing a loud frat, nothing happens and your rump area just feels a little itchy. Scratching your head, but feeling much better, you go back to talking with Arianna. She smiles when she sees that you're feeling better. But a few minutes later, the pressure builds again. Rather than hold it in, you let this one go. Your rear feels considerably more itchy than before, but you continue on as normal.
This happens several times as you wait... and wait.... and wait for your cake. The itching gets worse, but you start to notice that your pants are feeling just a bit too tight. Like you're wearing pants that are half a size too small. But you push this into the back of your mind As the date with Arianna gets better and better. You notice she's looking at you more rather than out the window, and that she's actually interested in what you have to say.
The pressure builds again just as Mandy finally comes back with your cake. She slams it down between you too as it builds higher and higher. As she smiles, her eyes flicker for one second towards you. Did her smile just get more confident? Like one of... triumph? You can't tell, but when she leaves, you notice she has a slight spring in her step and seems in a much better mood. As Arianna forks into the cake, you realize you've been holding the pressure all this time. You let it go... and almost gasp in shock.
You actually feel your rear expand in size and become itchier than before. It feels very tight against your pants, which now feel two sizes too small. You look back fleetingly and notice your pants are straining to hold your giant rear in. You also feel something, like a small nub, pushing against the back.
"Aren't you going to eat any cake?"
Arianna's voice brings you out of your fog of shock. "Uhhh...I'll be right back.." you say, getting up and walking backwards towards the waiting room. Arianna looks puzzled, but rolls her eyes and smiles and goes back to eating her cake. You, meanwhile, rush into the single bathroom in the lobby and lock the door hurriedly. You're about to pull down your pants and inspect your rear end when you feel the pressure building again.
This time, knowing what the gas does, you lay on the clean white tile of the floor, knees bent, back down, holding yourself up flat on your forearms. You try and hold it in as the pressure builds higher and higher. You beak out in sweat and almost pant at the effort of holding it in. Over the next several minutes, it builds higher and higher until it feels like you're about to give birth to a bowling ball.
You hear the doorknob rattling. You look up in shock and are thankful you locked the door. "Blair?" Arianna's voice calls from the other side. "Are you all right?" "Yeah, I'm fine..." you manage to pant out. "Well, I paid and I'm going to wait out here for you. It's shame you didn't get to taste that cake, it was really..." but the rest of her words are drowned out by the haze of effort of holding it in.
All of a sudden, your arm slips, and one shoulder hits the floor, accidentally letting go of the pressure and the silent gas. Your rear explodes in size, ripping your underwear and the seat of your pants to shreds. A tail shoots out of the base of your spine and hangs limply between your thighs. You look back and see your gigantic rump. You feel your tail flicking behind you. You realize, with horror, that you now have the ass of a...