Who needs water when you have cum?

"First thing first, we need to see if there's anything to drink. I've read that a human can survive a long time without food as long as they get enough water", you explain. Mariko pipes up:

"Yes, it's the survival rule of three - three minutes without air, three hours without shelter, three days without water, three weeks without food", she explains. "Though obviously it's just averages, like nobody survives three hours in a blizzard while here we probably don't need any shelter until the Monsoon rains start", she continues. Shelly gives her a curious look and the Japanese beauty shrugs:

"I read a lot", as if that's a sufficient explanation but there's time to question her more later.

"Right, so let's see if we can find a spring or something", you say and open Mariko's bag. Everyone gets their few clothing items and, most importantly, their sandals. Any hope of the crewman being wrong about the status of the island is dashed as you to the top of the beach and see nothing but thick jungle.

"Hey, I'll climb up there to that ridge line, maybe I can see something", Mariko says as she points to the rocky wall that surrounds the cove. If she can make it to the top, she should be able to get a good view around. You're little uncertain of sending the lithe girl to do that alone but before you can voice your concerns, your sister butts in:

"That's a great idea Mariko! We'll wait here for you to get back so we can decide which way to go", she explains. Mariko nods and takes off, carefully climbing over the rocks and the vines. You watch her go and she seems confident in her movements, so you turn to Shelly, one eyebrow raised in curiosity of what she's really planning.

Instead of explaining, Shelly squats down in front of you with a sigh of 'finally' and whisks your shorts down with two hands. Before your incredulous eyes, she inhales your soft dick in her mouth and proceeds to wrap her agile tongue around it. One of her hands slides down to hold your nuts while the other slides inside her bikini bottoms.

"Oh, damn Shelly", you moan as your cock hardens in her mouth. "Just make it quick, she'll be back soon", you say as your hands dig into your big sisters' hair. She wastes no time, bobbing her head and moving her tongue while applying pressure to your balls. You didn't think you were an exhibitionist but the thrill of getting a blowjob while waiting for Mariko to return is definitely there - especially with the illicit aspect of **** mixed in. It's a heady feeling that gets your engine revvin' in no time.

"Suck that dick, you sexy sister-slut", you curse, your mind clouded by a haze of horniness. In no time at all Shelly is bottoming out on your cock, her nose digging into your stomach. She's not done, of course, and pulls her head back, her lips leaving a snail trail of saliva on your shaft. You can't stop your fingers from firmly digging into her head as your horniness demands you take control. Naturally, Shelly doesn't mind, your mind manipulation has made sure of that. You repeatedly slam her face into your crotch, the gak-gak-gak noises she produces turning you on even more.

"FUUUUUUUUUUUUUUCK", you shout as you pull her head one final time against you, your engorged cock erupting straight down her throat. Shelly pulls against your hold and you relent, allowing your sexy sister-sucker to taste your cum. She looks at you with watery eyes as her mouth fills up. In one final act of perversion, she lets your dick fall out of her mouth, showing how full it is of your man-juice, then theatrically swallows it all down, ending with a cute AAAH-noise as she shows off her empty mouth.

"Who needs water when you have such delicious cum", Shelly says as she stands up and hugs you, her hefty bosom pressing against your chest.

That's when Mariko pipes up:

"Well, that's good then because I didn't spot any water at all, just kilometres of jungle", the petite girl says calmly.

Uh-oh, you're busted.