“Wow, this is so cool!” Emily chirped, squirming and wiggling excitedly on Emma’s couch. “It’s all, like, you know… So sciency and stuff!”
“Yeah, you’ve already said that about a hundred times, sis…” Emma mumbled, tightening the belt of her fluffy white bathrobe as she glanced to her side at Emily with a mix of perplexity and big-sisterly worry.
Emily was wearing only a skimpy silk robe that barely hid her breasts and groin, while leaving most of her huge round bubble-butt exposed. Even though Emily had reacted with enthusiasm when she had told her about Dr Jung’s research, Emma doubted that her ditzy little sister fully realized what she was actually signing up for. While Emily kept playing excitedly with her hair, which were blonde like Emma’s own but longer and cut in a cute bob, Emma wondered yet again if she should clarify things one more time for Emily’s benefit.
“Look, sis,” Emma slowly said, staring into Emily’s giddy eyes, “you don’t have to do this, really… I mean, the extra cash is great and I’m glad that you wanna help, but these guys are coming here to have sex, and lots of it. I know them, Ems: they are really into anal, they have massive cocks and they’ll want to fuck us silly in every hole until they can’t cum anymore. Our role in Dr Jung’s research is to ‘observe and report’, and that pretty much means that we’ll just have to let the guys do anything they want to us. And I mean literally anything, sis… So, if you’re having seconds thoughts just tell me now and I’ll handle it all myself. Okay?”
“Uh?” Emily said, blinking in stupor and furrowing her brow for a moment before laughing it all off. “It’s okay, Emma, it’s gonna be fun! I’ve even lubed up my butthole real good like you said! And remember back in high school? My biology teacher always said that I had a grade A ass! So, like, I’m the perfect gal for this!”
“Actually, sis, what Mr Gurth said was that the only way for you to pass his class was to have sex with him, and that he’d give you an A if you let him have your ass…” Emma pointed out, casting a resigned sidelong glance at her little sister.
“Oh, yeah, that’s right! And that’s what I did it, remember? He really gave me that A in the end too! Pretty cool, uh?” Emily concluded with a triumphant smile to which Emma could only reply with a forced, helpless grin.
Before the two sisters could say anything more, the doorbell rang.
“That’s it, sis,” Emma said, turning to Emily while standing up and heading to open the door, “last chance to back out…”
“Nope, I’m all in!” Emily beamed, jumping to her feet and undoing her flimsy robe, thus revealing her ripe pointy tits and her shaved little pussy.
Moments later Emma returned, followed by two young men that Emily sort of remembered meeting once before, at the nude beach. One was tall, blond and boyishly cute. The other was dark-haired and had an inquisitive glint in eyes, whose almond shape betrayed his Asian heritage. Dressed in T-shirts and jeans, both teenagers had toned physiques and sported visibly bulging crotches. Emily faintly recalled Emma telling her that they were seniors at the high school where she was a part-time teacher, but, beside that, Emily was totally drawing a blank.
“Guys, you remember my little sister Emily, right?” Emma said as the two boys smiled goofily at the sight of Emily’s semi-naked form, their hungry gazes zeroing in particularly on her voluptuous ass. “Sis, Simon and Makoto here will be our, uhm, partners in the research today. I’ve already explained everything to them and they agreed to keep this just between us.”
“Oh, okay,” Emily nodded as she cheerily waved hello at the newcomers. “Hey guys!”
“Hi, Emily,” said the blond one, Simon, apparently. “Wow, y-you have the same eyes as Emma, one blue and one green! I d-d-didn’t notice that back at the beach…” he stammered while stepping closer to Emily with an expression of mixed coyness and arousal on his face. “You l-l-look awesome!”
“Aw, that’s so sweet! Thanks, Simon!” Emily cooed as the young man stood in front of her, trying to look her in the eye yet unable to remove his gaze from the thick protruding curve of her booty.
Testifying to his arousal, Simon’s bulge just kept getting bigger, letting the contours of his massive cock show as it strained painfully under his pants, rearing to be set free like a caged beast. As if the prospect of fucking Emma and Emily to ‘help’ them with Dr Jung’s research wasn’t exciting enough already, the spectacular roundness of Emily’s bubble-butt was driving Simon completely crazy with anal lust. The fact that Emily’s tits were way smaller than her older sister’s mammoth jugs actually added to Simon’s horniness, because the regular size of Emily’s breasts emphasized to the max the incredible curvaceousness of her big, bouncy booty.
“Dude, back at the beach you didn’t notice Emily’s eyes because you were too busy ogling her ass!” Makoto snickered from the other side of the room, winking at Emma while Simon blushed and Emily tittered.