Mackenzie tried to appear natural as she strolled along the sand in Myrtle Beach. It was hard to do though, particularly because she was wearing nothing but a thong and a loose knit poncho. The rough cotton of the poncho irritated the nipples on her flat chest and she felt like a slut walking around with her ass hanging out.

The ten year old gritted her teeth. She looked behind her and saw her older sister, Allison, following several yards behind her and trying not to laugh. Mackenzie sighed. Allison was fifteen and she loved bossing her little sister around. This time, though, Mackenzie felt that things had gone a bit too far.

Three weeks ago, Allison had caught her younger sister masturbating. That was embarrassing enough already but Mackenzie had been pleasuring herself with a tampon when Allison busted her. The ten year old girl couldn’t help herself: she was very sensitive down there and she loved the feeling of anything in her vagina. Mackenzie had been slowly penetrating herself with the tampon for almost ten minutes when Allison burst into the room.

What followed was a lot of yelling and teasing and begging and tears. In the end, Allison essentially blackmailed her younger sister. Their family was going to take a short vacation to Myrtle Beach soon. During that time, Mackenzie was going to be Allison’s slave.

“You’ll have to do whatever I tell you,” Allison told her.

“Anything you tell me?” Mackenzie questioned, her eyes red from crying.

“Anything,” Allison told her. “And to show you how nice I am, here’s a deal: mom and dad will be at a conference every afternoon for three hours when we’re in Myrtle Beach. You only have to be my slave for three hours each day.”

They shook hands on it. Mackenzie didn’t really have a choice. And now, here she was on the first day of their vacation wearing slutty clothes that Allison had chosen for her. Thankfully, it was a cloudy day and the beach was relatively deserted for late August. Mackenzie was glad. No one had noticed her yet which was surprising because she was a very pretty girl. Mackenzie was rather tall for her age and her limbs were long and slender. She moved quite gracefully when she walked, thanks to several years of ballet classes. Her honey brown hair was perfectly straight and it hung past her shoulders in thick tresses.

The ocean breeze stirred and Mackenzie felt the poncho flapping around her. Alarmed, the young girl tried to hold it down against her body. It was a loose knit poncho and it was impossible not to notice she wasn’t wearing a shirt underneath. More importantly, the poncho hung low enough so that it offered at least a little coverage of her g-stringed rear.

Allison came up behind her. “Girl!” she exclaimed. “Look at you, showing off your cute ass to everyone!”

Mackenzie scowled. “Shut up, Allison.”

Her sister laughed at her. “Come on, this place is dead. Let’s go someplace where there’s lots of people so you can really show off.”

Mackenzie kicked at the sand. “Do we have to? I’m embarrassed enough already.”

“Three hours, Mackenzie,” Allison told her. “We agreed on three hours for every day. And it’s only day one! Two more days after this!”

Mackenzie tried to ignore her sister’s taunting. Allison took her hand and led her away from the shore to where a well-touristed cluster of souvenir shops. They left the sand and got on the boardwalk. A family four walked by. The mother was too busy with the bickering kids but Mackenzie saw the father do a double take as they passed.

Allison noticed too because she snickered. She glanced behind them. “Hey, he’s still checking you out!” Allison crowed. “Let’s give him a better look…” So saying she lifted the rear of the poncho, revealing Mackenzie’s thong.

“Allison!” Mackenzie shouted, realizing too late what her sister was doing. She slapped Allison’s hand and moved away from her sister. Mackenzie fumed as Allison cackled, clearly enjoying her little sister’s humiliation.

There was a much more people on the boardwalk as compared to the beach. Mackenzie pretended not to notice the stares of passers-by. Some people didn’t notice but she could feel the eyes of many more people who did notice her bare skin underneath the poncho. A group of teenage boy walked by and Allison could see them snickering and elbowing each other. Miserably, Mackenzie crossed her arms across her chest.

Finally the reached the end of the row of shops and Mackenzie ducked into an alley. “Allison!” she protested, “I don’t want to do this anymore! Can’t you do something else? Please?”

Allison rolled her eyes. “You’re such a baby,” she said. “Maybe you should have thought twice before fucking yourself with that tampon.”

“Shut up!” Mackenzie hollered, punching Allison in the arm.

“Oooh, oh yeah, that plastic feels so good!” Allison said mockingly. “How was it to lose your virginity to a piece of plastic?” She burst into an uncontrollable fit of laughter as she dodged Mackenzie’s fists.

“Tell you what, Mackenzie,” Allison said, her face becoming serious. “Here’s a deal: I’ll let you off the hook for the rest of the vacation if you can do one thing.”

“What?” Mackenzie asked suspiciously.

“You have to rollerblade up and down the boardwalk three times.”

“That’s it?”

“Yes. But you have to take off your thong. All you can wear is the poncho.”

Mackenzie blinked. “What? That’s not fair!” she protested. “I’ll be totally naked!”

“That’s the whole point,” Allison said, smiling easily.

“What if people notice I’m naked?”

“It’ll be exciting for them and for you,” Allison told her. “Come on, Mackenzie. It’s less than five minutes of possible embarrassment but then you’ll be free for the next two days. What do you think?”

Ten minutes later, the two sisters returned to the boardwalk, Mackenzie clutching her rollerblades. Again, they ducked into a narrow alley between two stores. “Remember,” Allison said. “You have to rollerblade the entire length of the boardwalk, here and back, three times.”

“Okay,” Mackenzie said, pinching her lips in apprehension.

“Give me your thong,” Allison ordered.

Casting a quick glance to make sure no one was coming, Mackenzie quickly stepped out of the thin underwear. She then bent over to put on her rollerblades but Allison stopped her.

“Nope,” she said. “You have to put the rollerblades on out there, on the boardwalk.”

“You never said that!” Mackenzie complained.

“Just do it,” Allison warned, “or the deal’s off.”

Frowning, Mackenzie stepped out of the dark alley onto the busy boardwalk. Several families were walking the promenade, parents enjoying the afternoon with their strollers and kids in tow. The young girl felt very conspicuous wearing nothing but a thin poncho in public. Mackenzie searched the boardwalk for a bench where she could sit down but there were none.

Instead, she bent over and began jamming her foot into the rollerblades. But the problem was that as soon as she bent over, her poncho hiked up a bit, revealing her bare bottom underneath. It had felt strange when her butt was exposed in the open but it felt even stranger now that the ocean air was tickling her bare privates.

Mackenzie scanned the boardwalk, looking for a break in the stream of traffic. She needed to bend over to put on the rollerblades but she didn’t want to moon anyone. It was useless though. The promenade was simply too crowded with people walking by her every few seconds. The best she could probably do was to stand with her back to the storefront, facing the ocean, and hope that no one inside the window was watching.

Swallowing hard, Mackenzie turned to face the ocean and bent over, pushing her slender butt into the air as she wiggled her feet into the rollerblades. It took several seconds for her to close the straps to the rollerblades. Finally, she righted herself again and stood up. Mackenzie glanced behind into the storefront window and was mortified to see two elderly ladies looking at her with a severe expression of disapproval. The preteen girl blushed a bright red. Wishing she could disappear, Mackenzie began to rollerblade down the boardwalk.

“I should try to do this as quickly as possible,” she thought to herself. “Just get it over with so Allison will stop blackmailing me.” She strengthened her strides and picked up speed. The problem was that the faster she went, the higher the poncho fluttered in the wind. The air rushing against the bare skin of her crotch reminded Mackenzie of her predicament.

She zipped by a man and woman pushing a stroller. “Oh my god,” she heard the woman say as she passed. Mackenzie glanced down at herself and realized with horror that the poncho hem had fluttered up past her belly button as she rollerbladed. Anyone could see now that she had wore nothing underneath. Not stopping, Mackenzie grabbed the front of the poncho and yanked it down.

It was awkward but she managed to keep on rollerblading as both hands carefully held the front hem of the poncho tight against her crotch. Her butt was still on display, of course, but Mackenzie decided that was inevitable.

At last she reached the end of the boardwalk. She did a quick turn and began the return trip. It was worse this time because she recognized the faces of some of the people she had passed before. Some were shocked at the preteen girl, others actually seemed interested, which made Mackenzie even more embarrassed for being such an exhibitionist.

She passed two teenage boys, also on rollerblades, who were going the opposite direction. They must have turned to watch her as she passed because Mackenzie heard catcalls and whistles of approval. The ten year old girl gritted her teeth and kept rollerblading, making sure to keep her poncho hem covering her bare crotch.

“Hey baby, what’s going on?” a male voice behind her asked. Mackenzie turned to find the two teenagers she just passed, now rollerblading right behind her.

“Damn, look at that little ass she has on display,” the other teenager said. Mackenzie’s ears burned with shame.

“Are you out to get some honey?” one of the teenagers laughed.

“Leave me alone!” Mackenzie called angrily over shoulder. She tried to speed up but the older boys easily kept up with her. One of them moved in close and put his chin on her shoulder. He was rollerblading so close that Mackenzie could feel his chest against her back.

“Stop it!” she shouted furiously. Instead, the ten year old girl was shocked to feel the boys hands squeezing her bare butt.

“Mmm mmm, this girl is ripe!” he laughed at his friend as he caressed Mackenzie’s smooth cheeks. Then, unintentionally or not (Mackenzie couldn’t tell), his finger slipped into her dark ass crack.

The sensation of his finger probing against her anal rosette made Mackenzie yelp. “Quit it!” she shrieked loudly. The boy, surprised, immediately backed off. Mackenzie began sprinting as fast as she could on her rollerblades, leaving the boys behind. Her arms swung confidently with her strides now and she made no attempt to hold down the fluttering poncho.

Mackenzie’s face was red from exertion and embarrassment when she reached Allison, who hadn’t moved an inch from where Mackenzie left her. Tears stained the young girl’s cheeks.

“This guy just felt me up!” Mackenzie wailed, bursting into a new set of tears. “I don’t care, I want to go back to the hotel room. Give me my underwear back…” Without waiting, she grabbed Allison’s purse and retrieved her underpants.

Allison tried not to suppress a smile as Mackenzie moved into the alley to get dressed. “Well, I’m sorry that happened,” she said smirking. “You do realize that you still have to do everything I tell, right? You didn’t finish rollerblading.”

“I don’t care,” Mackenzie said, sniffling.

“I just wanted to remind you, that’s all,” Allison said. “I can’t wait to dress you up tomorrow.”