Neither

Immediately after both James and Shiro have said the sacred word, several things happen. Shiro, Dove and Wren's bellies are all filled to the brim with a liquid, presumably milk. Everyone can see that this is the case, even the men, since the women's bellies visibly expand, so that they look seven month's pregnant! When Sora said "to the brim", it's clear that the universe took him literally.

"Holy shit." Dove squeaks.

"Oh my god!" Wren yelps. "I can't hold this in for long-MMMF!"

Wren and Dove are both shut up by the appearance of cloth gags in their mouths. At the same time, blindfolds appear over their eyes, and ropes appear around their bodies, yanking them to the ground and tightly binding them in a kneeling position. They can't move a muscle now, both with heads down and asses up, bellies distended and full-to-bursting. All they can do is moan, panicking, into their gags, and do their best not to be the first to expel over two ounces of the contents of their guts.

And so the game has begun. Shiro has to silently choose which butthole to approach and hover her mouth over, so that she can catch the enema that comes out and win the game.

"You'd better hurry up, little bird." James taunts. "It's not going to take long for one of you to burst!"

Shiro ignores James, and looks to Sora, who smiles and nods to her knowingly.

Shiro stares daggers back at her brother, as if she understands but isn't particularly pleased. Still, she starts moving.

...But she doesn't get on her knees and crawl over to one of the two slaves. No, instead she goes over to the nearest wall, and lies on the floor in front of it, with her feet touching the wall. Then she slowly begins to shift her feet up the wall, shuffling her back foward as she goes, until her legs are vertical, leaning against the wall, and her butt is touching the wall at the bottom.

"What the hell is she doing?!" James cries.

"Normally she would be flexible enough to do this without the wall." Sora says calmly. "But with the giant belly, I guess she needs the extra support."

"This doesn't make any sense, though! What's she doing?!" James continues.

Shiro is now inching her butt up the wall, using it for support, until the only parts of her body touching the floor are her head, neck and arms.

"Are you hoping that being mostly upside down will allow gravity help you to keep the milk inside?" James asks. "You must be more stupid than you look! You still lose if one of the other girls lets loose and you're all the way over there!"

Sora shakes his head. "I made sure to work a little loophole into the rules, and Shiro noticed immediately. Unforunately, you didn't."

"W-what do you mean?" James sounds very worried now.

Shiro pushes her feet away from the wall, and bends her knees. Her knees lower down until they are on the floor either side of her head, and her butt his now the highest part of her body, with the rest of her bent over double. She's in a sort-of piledriver position.

James finally begins to understand. "You're going to push your own enema into your own mouth to win?! But the rules we agreed on state that you lose if you are the first one to expel your enema!" He complains.

"Not quite." Sora explains quietly. "The wording used was: 'Shiro wins if the woman who first expels her enema, expels it into Shiro's mouth. Otherwise, she loses, including if she expels two ounces of her own enema first.' All Sora has to do is get at least one ounce of the first two ounces that leave her into her mouth, and she wins before she loses."

"What?! That's not the game I agreed to-"

"That's exactly the game you agreed to." Sora interrupts James.

And then Shiro begins to push out her enema.

It's not an easy task, aiming your anal milk foutain at your own mouth, but if anyone can do it, it's the expert of angles, the young woman known as Sora.

SPURT SQUELCH RASP

It sounds horrible, and looks even more outrageous than it sounds, but Shiro's aim lands true. An almost perfect arc of milk sails from her butthole and into her mouth, where it lands with a loud wet pitter-patter.

"Yuck." Sora can't help but comment, wrinkling his nose.

"Nooooo!" James has bigger concerns.

Click! Clank!

The sounds of mechanical locks turning are followed by the sounds of Dove and Wren's metal collars hitting the floor. The rest of their bondage vanishes into thin air. At the same time, the piece of parchment detailing Shiro's bonus forfeit disappears into thin air. The game has concluded, and Shiro is the winner.

Dove and Wren are free, and James no longer owns any slaves.