Tiny Spaces with Sister

It's all fun and games until someone's cock becomes out of control for medical reasons. Especially if that someone is in the family.

Genevieve learned that the hard way.

What began as a family trip to Thailand turned into something else when they went to an exotic beach. Her parents were the brainy types, so they spent their morning with a group of other tourists and a Thai tour guide who was an expert in local geology and the ecosystem.

She and her brother, however, were ordinary college students with ordinary college needs, looking to swim and have fun. Genevieve wore a sexy bikini. Mike wore swimming trunks. They'd been on plenty of family vacations together so they were used to seeing each other in swimwear.

They did some light swimming in the shallow end of the water where the waves hit the sand, getting warmed up for a deeper swim to follow.

"Feel like a race?" Mike grinned.

She grinned back. "Name it."

Being on the college volleyball team had really honed her physique over the past year. She was certain it would give her some kind of competitive edge in their everlasting sibling rivalry. She always loved putting her brother in his place, but it was only occasionally that she got to be the victor. Today, she was in an energetic mood. Confidence was flowing through her blood. Yes, she was up for any challenge.

"Let's see who can swim against the tide fastest," he said, pointing to where the water changed color. "Just up to there. Nothing dangerous. Then we swim back."

"What if I win?"

"You won't. But the winner gets to sleep on the bed next to the window for the rest of the trip. No more alternating."

"Hmm..." she pretended to think. "You're on!"

Genevieve dove into the water first and went full force against the oncoming waves. All that working out at college was really paying off. She didn't have to check if her brother was on her tail; but she knew he wasn't far behind. They were both competitive, afterall.

When she came up for air, she saw that her brother was catching up with her. She pushed harder. She had to win this.

Unfortunately for Genevieve, her brother's strength and stamina gave him a big edge. She had better technique, but Mike had better muscles. He won this time, but Genevieve was right behind.

The race ended further from the starting point than anticipated, and they were both gasping for air.

"Lucky you," Genevieve said laughing as they trod water.

"Damn, you're getting good," he said back, still gasping for air. He glanced over Genevieve's shoulder. "Holy shit. Look over there."

They looked to the right and saw a series of massive rocks and boulders which appeared to have formed a small hill. It was unlike anything they had ever seen back in America.

"Isn't that where Mom and Dad went?" Genevieve asked. "On that tour."

"I think so. It's kind of dangerous apparently, so if you're not a local, you have to go with a tour guide."

Genevieve couldn't take her eyes off it. "What's so dangerous about it?"

"Caves, I think."

"Bummer. We should have gone with them."

"We can still go," he said deviantly. "It'll be our own private tour."

"Sure, if you're up for it," she replied, quick to rise to the challenge.

"I am. But can you swim that far?"

She splashed water at his face. "Let's go slow this time. My heart is still pounding."

"Mine too."

They swam side-by-side, at a much more leisurely pace. The closer they got to their destination, the more excited they became. This was what Thailand was all about. Adventure.

After a 15 minute swim, they were almost there. Their arms were tired but they knew they'd be okay after some rest when they reached their goal.

"I don't see anyone," Genevieve said as she emerged from the water. "It's kind of scary here."

"Who knows. They might be in a deep cave somewhere. There's a number of them if I'm not mistaken."

"I'd love to have a peek. I've never seen a cave before."

"Ahh!!!" Mike hollered suddenly. "Shit!"

He jumped up as soon as he reached the shore and limped out of the water.

"That's not funny!" Genevieve screamed.

"Something bit me," he said as he inspected his left thigh.

"Really?"

"Look."

Genevieve could see two small holes on his left thigh. The skin was red but it wasn't bleeding.

"Jesus. What the hell was it?"

"I didn't see it," he replied. "It stung me and swam away."

"Should we swim back to the resort? It might be serious."

"I need a little rest before I can swim back. How about you?"

"I need rest too," she said.

"In that case, we might as well check out a cave while we're here. It beats sitting around doing nothing."

"Can you walk?"

"My leg feels fine," he replied. "It's probably nothing."

Genevieve grinned, eyes sparkling. "In that case, I'll race you!"

She immediately positioned herself to sprint to the nearest cave.

"Hey! Same time!" Mike said.

"I'm only joking. Come on, let's stroll to that cave over there, then we can go back. I'm worried about that bite. We should get you some treatment. Afterall, we don't know what it is."

They walked over to a nearby cave entrance. It was a small one. Narrow. There was light shining inside, so there were probably other openings.

After a short while inside, they came to a dead end and saw a hole down on the bottom of a cave wall. It appeared to be well lit on the other side of that hole.

Genevieve bent down to peer through the hole.

"What's on the other side?" Mike asked.

"It looks stunning," she replied. "I don't know how to describe it, but it looks like a pond with these crystal things which naturally formed from the top. It seems like sunlight is filtering into the space too."

"Well, let's squeeze through the tunnel and go have a look."

"Are you sure you'll fit inside? Because I know I'll fit in there. I'm lean and slender. You may be in shape, but you have broad shoulders and muscles."

Mike knelt down beside her and peered inside. "It'll be super tight, but I'll fit. It looks amazing in there."

"You're sure you'll fit?" she persisted. "You're sure, sure? Positively sure? Because if you get stuck in that tunnel, we're screwed."

He kept analyzing with his eyes. "I think I can make it in. I'll go first. If I get stuck, which I won't, then you can pull me out."

"What a joy."

"Here it goes."

Mike crawled on the wet surface and made his way into the tiny space. He held his arms forward and exhaled in an effort to make his body slimmer. He felt as though the air was being squeezed out of his lungs at one point, but he made it.

Once on the other side, he stood up and breathed deeply. Then he looked down again.

"Are you coming?" he asked through the hole. "It's really amazing in here."

"Yeah, hang on."

Genevieve performed the same maneuver. It took much less effort, but it was still a mission. While her slender hips and torso were an easy fit, her tits felt plenty of discomfort as they pressed against the rocky surface.

Once they were both inside, the siblings marveled at the exotic cave. It was unlike anything they had ever seen on tv. They seemed to be in the midst of a cave complex. It was like a maze. There were cave entrances in all directions.

"Let's not even think about exploring more," Genevieve said. "We'd get lost."

"I know. This is overwhelming enough. God, look at this place."

Their eyes marveled at the structure which was created entirely by nature. They took a few moments to walk around the pond area and peek inside several of the cave and tunnel entrances. It was simply majestic.

"Ouch," Mike said suddenly, limping a little bit more.

"Are you okay? Is it hurting?"

With concern, she touched her brother's bare shoulder, holding on to him to make sure he wouldn't fall.

"I feel weird," he said. "I don't know, it's like a pressure is building up inside of me."

"Can you swim back?"

"I think so."

"Shit," she said. "We better go before your leg cramps or something. We'll swim close together. If your leg hurts too badly, then I can help you swim on your left side."

"Thanks. You're the best."

They went back to the tiny tunnel from which they came. Mike went first again. He lowered himself, kept his arms forward, and got ready to slither back to the other side.

Everything seemed to be going smoothly--- until he was halfway through. He gave a small yelp of pain.

"Are you okay?" Genevieve asked, keenly aware that something was wrong.

"Pull me back! Pull me back!" Mike was shouting in desperation.

She grabbed her brother's ankles and did her best to pull him out of the tunnel without hurting him. Mercifully, the retreat was smooth.

"What happened?" she asked.

"It's nothing."

Clearly it was something. He adjusted his swimming trunks on the front side. Then he positioned himself to try again. This time, he sucked his chest and stomach in deeper in hopes that it would help.

He crawled in the tiny space again, and when he reached his waist, he found himself stuck for the second time. He kept trying to push and wiggle his way through, but something was stopping him.

"Pull me back," he said in defeat.

Genevieve grabbed his ankles and gave a hard tug to pull him out.

"What happened?" she asked. "It's so weird. You were able to come in easily. Why can't you get out?"

"Trust me, you don't want to know. I'll try again."

As he sat on the ground, he adjusted his swimming trunks more thoroughly this time. He dug his fingers in the front and shifted things around.

"Are you... hard?" she asked, which sounded more like an accusation.

"What? No. Are you kidding?"

He sat there, still having a hard time adjusting himself.

Finally, he confessed. "A little. I don't know what's going on. It's like, I'm not aroused, but there it is."

He gestured down to his crotch area.

Genevieve raised an eyebrow. "You're not aroused, but your dick is hard?"

"You wouldn't understand."

"You're right. I don't. All I know is that caves are dangerous places, you've already exerted a lot of physical energy by swimming here, and now you're sporting an erection?"

He scoffed. "You think I'm doing this on purpose?"

"Are you?"

"Let's just try again," he sighed.

"No. Not yet. I don't want you to hurt yourself. I mean, is your dick really so big that you can't squeeze through?"

"It's decently-sized," he answered through gritted teeth, almost offended that she'd ask something like that. "Trying to squeeze through hurts like hell. Just imagine a rock being pressed tightly against your... nevermind. You get the idea."

"I can imagine. The rough surface was tough on my breasts too, but it was still much easier for me to fit."

"Should we try looking for another exit? There's light and plenty of other caves."

"No way, I'm scared," she said firmly.

"Yeah, it is pretty scary."

"So is it... are you... still hard?" she asked cautiously.

He sighed. "It's throbbing, actually. I also feel kind of light-headed, like my blood pressure is high."

Genevieve squinted her eyes as she thought. She had taken plenty of health classes in college and had read countless articles on the human body over the years.

Suddenly, it came to her.

"Holy crap, Mike, do you know what this means?" she exclaimed at last.

"What?"

"That bite. Whatever bit you might have released a toxin in your body which is causing your erection. I read about something similar happening to someone after an insect bite a few years ago."

He checked his wound. "Oh shit, you're right. Look."

The punctures on his thigh turned even more red, but still wasn't bleeding, suggesting that something had indeed been injected into him.

"Now what?" she asked.

"I don't know."

"Should I swim back myself and bring in the experts?"

"Do you realize how humiliating that would be?" he asked. "Besides, I think it'll go away soon."

"You wish. According to that article, the erection could last up to four hours."

"Damn, are you serious?"

"You tell me," she said. "It's your cock. You still look flustered."

"It's still aching."

"Can you walk?"

He nodded. "Sure, but it would look... ummm... humiliating."

Genevieve suddenly giggled at the embarrassing image of her brother having to walk around with a hard cock bulging through his swimming trunks.

"Too bad," she said, amused. "We have no choice but to try and find an alternate route. Nothing dangerous. But I'm sure there's a safe way out of here. Then we'll swim back to the beach. I hope your 'issue' won't hamper you while you're in the water."

"Very funny. Are you going to turn around?"

"No."

"Why not?"

"You might fall," she said. "I'm your medical supervisor now."

"Your choice."

Mike stood up and there was a blatant bulge in his shorts. The head of his dick poked out and his shaft was outlined against his wet swimming trunks.

"Hmm..." Genevieve said, almost licking her lips.

He covered himself with his hands. "Let's go."

They decided on the nearest cave for their first attempt at finding a proper exit route. There was some sunlight, so hopefully this would lead outside. All the while, Genevieve was smirking and looking back to steal glances at her brother's bulge, making him blush and do his best to hide it while walking.

She stopped in her tracks suddenly.

"Wait," she whispered. "Shhh..."

They stood still for a few seconds. Neither of them made a sound.

"What is it?" Mike whispered in a low voice.

"I thought I heard something."

They kept quiet a few seconds longer.

A faint sound echoed from the caves:

'...all of which formed thousands of years ago...'

Their eyes widened when they heard the voice.

"The tour guide?" she whispered.

"I think so."

"But where?"

"It's an echo," he replied. "They could be anywhere."

"We could shout and try to join their group?"

He pointed to his crotch. "Imagine if they saw this. They'd think I'm a pervert."

"But your health, Mike. The tour guide might be able to assist."

"I have a really hard erection. Mom and Dad might think we were having sex inside this cave if they saw me like this."

Genevieve's jaw nearly dropped. "Crap, you're right. Quick, let's go back."

They rushed back to the tiny space from which they came. Unfortunately, the small hole was the same size, and Mike's erection was still bulging.

"I'll just sacrifice myself," he sighed. "You swim back to the shore yourself. I'll try to meet up with the tour group and explain that a creature bit me."

"Yeah right. We're supposed to stick together. Mom and Dad know that we wouldn't separate. Not in a foreign country. We'd certainly split up in America, but we'd never split up in Thailand."

"You're right."

"Now what?" she asked.

"I need to try again."

"Would it hurt?"

He nodded with a fearful look on his face. "Of course it's going to hurt. But I'll have to find a way to squeeze in."

"What if you... you know... take care of it?"

"Huh?"

"Jerk off and cum inside the water to hide the evidence. Would that do the trick?"

He blushed. "It could. Did you read about that in the article you mentioned?"

"No. The article made no mention of relief. Just that the erection lasted for hours."

"You should crawl out and wait outside. I'll relieve myself, then I'll follow you."

She raised an eyebrow. "But what if it doesn't work? You'll be stuck here by yourself."

"Good point."

"Just cum," she said bluntly. "It'll be fine."

"Are you sure?"

"I have another idea," she offered.

"Tell me."

"What if you removed your trunks and tried to squeeze through that small tunnel naked?"

"Are you kidding?" he replied in shock. "You know how much that would hurt?"

"Yeah, but think about how much space the elastic waistband of your swimming trunk takes up. It's like a centimeter or two. If you found a smooth surface and squeezed in at the right angle, I bet you could make it."

He thought for a moment, looking at the hole and thinking about the safety of his dick.

"Yeah, that could work," he said.

"Then get to it."

"But that means you'll see my dick and ass."

"Your balls too," she added.

He lifted an eyebrow. "You don't mind?"

"Like you said a moment ago, if Mom and Dad see this, they might think we were fucking in here."

"Oh god."

He stuck his fingers underneath the elastic of the swimming trunks.

"Need help?" she asked.

"I don't mind being naked. It might embarrass you more."

"Nonsense."

Genevieve reached over and yanked her brother's swimming trunks down. She expected to see a hard cock. What she didn't expect was a hard cock swinging back and nearly hitting her in the face. She moved her head to the side swiftly like she was playing dodgeball.

"Oh wow," she gasped. "That looks serious."

She stared at his cock, which curved upwards and was swollen to the point where it nearly turned a shade of red.

"I know. It's way harder than usual. Do you know anything about this?"

Genevieve inspected it closer. "Hmm. Wiggle it."

"How?"

"Move it, up and down."

Mike bounced up and down, moving his cock as his sister requested.

"Now side to side," she commanded.

Mike stood in place and continuously turned his waist so that his cock waved from side to side.

"Any thoughts?" he asked.

She grinned cheekily, "It's a super hard dick."

"Thanks for the doctor's note."

"Hey, I'm doing the best I can. Now let's get out of here. I'll assist you however I can."

"Fine, and remember, this is your plan."

"But it's your cock," she quipped.

"Touche."

Mike returned to the mission and looked for the smoothest surface. From the looks of things, the smoothest surface was at the top of the small tunnel.

"Bad news," he said. "I'll have to lay on my back. Less chances of injuring myself that way."

"Your call. Do it."

He hesitantly flipped onto his back and now his hard cock was pointing up. Any other time in life, this would have resulted in merciless teasing, but they knew this was an emergency. They'd cooperated well in the past on serious matters.

Isn't that what siblings are for?

Mike moved inside the small tunnel while on his back, arms forward, using his feet and hips to wiggle his way in. When he made it halfway, his cock was in danger of being squished, so he paused.

"A little teamwork would be nice," he said.

"Then teamwork it is. Here it goes. 3...2...1..."

Genevieve used the tips of her thumb and index finger to pinch her brother's cock. That thing was impossibly hard. It was almost like a steel pipe, she thought.

"Are you always like this?" she asked, pinching it. "Or is this purely the toxin?"

"Both. The randomness is the toxin, for sure. My cock just became crazy hard out of nowhere and it's not going away. That's the toxin's doing."

"Got it. I'm tucking you in now, so I'll be stuffing your dick inside the tunnel so you'll fit. Brace yourself."

She squeezed the whole cock with all her fingers and the palm of her hand and pushed it against Mike's stomach, in between the rocky tunnel. It was a struggle so she kept on pushing and working her hand on it.

"Umm... Geni?" he called out.

"Yeah."

"Are you touching my cock using my swimming trunks or your bare fingers?"

"Oh crap," she gasped. "I forgot about using your trunks to touch it. Oh well, my fingers are already busy."

"Well, okay, is it working?"

"Almost, I think. Wait, let me try something else."

She gave a hard push with the tips of her fingers to shove the cock inside.

"Ouch!!!" he hollered. "Are you trying to break my dick?"

"Sorry. And keep it down, would you? These caves echo, remember? Wait, hang on a sec."

Genevieve got up and went over to the other side of the cave. She kept her ears peeled and listened attentively to the echoes.