Matt (Mandi), Dan (Danielle) and Liam (Lisa) were a trio of high-school track athletes and friendly rivals who were constantly trying to one-up each other at high school in pushing their bodies to the physical limit, so when a New-You Body Change shop opened at the local mall in town they were already thinking of ways to use it. Dan, always a show-off, was bragging about how he could beat the others even as a girl, so the three decided their new challenge was going to be completing a 4000 metre run in cute female bodies. They’d even borrowed a few uniforms from their female friends and were dressing for the part. The losers forced to stay inside their humiliating, girly body for the rest of the week, so the stakes were high.

“See? It’s flat d-down there now.” announced Mandi nervously, lifting up her skirt to show off her skimpy silk panties. “I’m all-girl now.”

“Nice pussy, man-I mean, woman.” Danielle said, checking out her friend’s barely-covered vag before her eyes drifted up to her chest. “I mean, I know me and Lisa’s tits are big, but check those out...”

“Your tits are fucking huge, dude.” Lisa stated, reaching out and giving them a playful squeeze to check if they were real. “Like, giant first-prize melons. You sure you’re going to be okay with those?”

“Well, I thought that if I was going to b-beat you losers so easily...” Mandi stuttered, clearly lacking confidence. Feeling the heavy H-cup weight on her chest wobble with every movement she was beginning to worry she’d lose, and then she’d be forced to carry around the pair of back-breaking boulders on her chest for the next few days. She’d even had to buy an extra-large shirt to accommodate their size and they were so tender already, so she couldn't even imagine how busty women managed to do it every day. “...I’d do it with the biggest h-handicap too... Let's head to the track.”

Heading out to the starting line, the three lined up and psyched themselves to get ready for the race like they usually did, although this time the unfamiliar uniform and swinging breasts on their chests were incredibly distracting. A siren ringing out, the trio began to run down the track when they all realized that under their new center of balance it was difficult to maintain their pace, and their skirts were constantly riding up and showing off their asses to the quickly-amassing crowd of horny schoolboys who were gathering in the stands. Worst of all was their breasts... with no time beforehand to buy any bras between them they were wildly bouncing with every step, threatening to burst through their shirts as they wobbled and shook like crazy. Mandi, who was already regretting giving herself such giant knockers, could feel them slapping against her chin every few seconds.

All having overestimated their ability to perform in their new bodies, the race quickly became a competition to see who would give up first, and the gawking and cheering of the boys as they ran past was distracting. Mandi was just behind the pack when she tripped and fell, landing painfully on her chest as her shirt finally gave up, buttons flying onto the concrete as her enormous, soft, bare titties were exposed to over a hundred horny schoolboys!

Even though she was trying her best to maintain her modesty with her hands they were woefully unequipped to cover her gigantic boobs and could barely cover her raw pink nipples. People were already beginning to take photos. Tears began to well up in her eyes as she ran for the change rooms to hide herself, instinctively heading towards the men’s locker room where the senior men’s soccer team was getting changed - and they all loved the view too.

In the end, it never mattered who won the race: after running into financing troubles after a legal dispute, the New-You Body Change franchise was immediately shut down, their assets liquidated and anybody who was trialling a different body that day was trapped that way forever. From then on the three boys-turned-girls were forced to get used to their bodies and understand the life on the other side, including makeup, wearing feminine clothing, and especially bra sizes. And while they had to give up on their track careers, they were still just as competitive as ever at different types of sports instead: skimpy mud wrestling, flashing strangers at the train station, and competing to see who could get the others to cum first in their daily lesbian threesome.