One giant hotdogging for mankind...

Isaac, still lifted up by Luna's strong hands, was starting to feel a little woozy, both from being smothered in affection from these two demigoddesses and from having a mind-blowing orgasm on average once an hour for the entire second half of the day. It was hard to believe that his first spectacular day of having the Root of Honesty was coming to a close! Whatever doubts or misgivings he'd had about using and abusing this power back then, what felt like a lifetime ago, they were well and truly swept away by the tidal wave of pleasure and praise.

Still, he was only mortal... for now. "Fair warning, I might only have one more in the tank. It's been a heck of a day," Isaac remarked, putting a hand up to his forehead. "But hey... Pleasurably tuckering out your man gives you all a sense of pride, satisfaction, and group accomplishment, right?"

"Poor thing~," Luna cooed while patting his head, her faux-sorrowful pout betrayed by a slight smirk tugging at the corners of her lips. "Celestia really went all-out on you, huh?"

"To be fair, I also went all-out on her, too," Isaac admitted with a bashful laugh. "She actually asked for a break before I did."

The nine-foot-tall Princess shuddered from head to toe at that claim, entirely believable based on what she'd seen of her sister during the hand-off. "Such a studly hero..." she swooned. "Fucking my sister to exhaustion on the very first day of your candidacy...! But as much as I would love that same treatment, I'm glad that you are recognizing your limits, too. A good sign that you are in this for the long haul, not a mere sprint."

Isaac smiled happily, his cock slowly rising back up for one more round. "Well, if things keep going like they have for the past month, my stamina and size are only going to go up from here, heh heh!"

Luna gave his firming cock a quick kiss on the back of his shaft. "Then tell me... How shall we make tonight's final orgasm special for you? Feel free to request aaanything that comes to mind," she added with a none-too-subtle wiggle of her mindbogglingly humongous ass, her moon-splotch Cutie Marks stretched across their vast canvases.

The choice was lip-bitingly obvious. "I'm gonna have regrets for the rest of my life if I don't feel the ass of a goddess wrapped around my cock tonight."

"You flatter me~," Luna replied, and then bodily carried him back down to the bed, laying him roughly around the middle of her gigantic mattress. Now laying on the center, he could feel that the bed was dented slightly, no doubt from its occupant's heaviest anatomy weighing it down night after night! Isaac got comfortable and watched as Luna turned around, presenting her massive, perfect ass highlighted by the moonlight through the balcony window.

Just one of those cheeks was capable of covering most of his body, let alone both! Their sheer size and their contradictory roundness in defiance of biology was almost maddening! Celestia's tits had had the same ever-so-slightly mind-bending effect on him, like he was staring at a localized eldritch space where physics as he knew them were bent a little bit wrong. It gave their assets that little bit of an extra aura, of being powerful, of being far more than what mortals could achieve!

"Ah, Isaac! If I didn't know any better I would say you were play-acting the slack-jawed fool for my benefit!" Luna teased him, swaying her hips back and forth, making her ass wobble across a wide arc.

Isaac closed his hanging mouth and giggled. "Nnnope! Just an actual slack-jawed fool here."

"I'm glad we can return the favor for the awe your manly cock inspires in us~."

Luna then leaned forward and tilted back on her legs, setting her on course to CRASH onto the bed, covering the whole bottom half of the mattress in one fell swoop! Isaac would have been bounced right up into the air if his legs and crotch weren't pinned down by navy blue booty! As it was, his upper body was still pivoted forwards to crash into Luna's rump before falling limply back down! His cock, as huge of a third leg as it was, simply could no longer be seen behind the squeezing wall of Luna's booty cheeks!

The Princess giggled at his silly physical reaction, then started to gently wiggle her hips and grind them against the bed, making her firm-yet-yielding bubble butt wobble and twist around his cock. He could also occasionally feel her puffy asshole rub against the middle of his shaft. "Mm, we're at a crossroads, Isaac. Do you want to stuff me full, or is this motion by itself enough for you~?"

Now that was a tough choice. Fill her glorious hole or enjoy the sheer size of her cheeks? It all came down to a matter of preference. And as an absolute addict for titfucks, Isaac couldn't help but be drawn towards the act's southern cousin. He'd already enjoyed anal with Celestia, anyway, and that gave him an idea. "Celestia definitely loved me filling her up, but in contrast to her, you're more of an outercourse girl, aren't you? This world is nothing at all like my world, where vaginal or anal is the 'main event' and everything else is foreplay or a quickie, right? You've all been practicing the most likely acts your Master might want, but there's a wide variety of acts you enjoy, right? If I want just blowjobs for hours, or just hotdogging, or just to rub my cock all over a woman's body until I cum, that's just as valid as penis-in-vagina sex, isn't it?"

Luna blinked in modest surprise as she looked at him over her shoulder. "You are... astonishingly perceptive for someone completely alien to our ways. How did you learn such things about us so quickly?"

Caught once again with his 'too detailed' questions, Isaac shrugged bashfully where he lay. "I was in a strange alien world surrounded by impossibly sexy creatures at every turn, and I had nothing else to do while I worked up the nerve. So I went to Twilight's library and read up everything I could about relationships and sex in this world compared to mine. That makes sense, right?"

"Oh, of course!" Luna replied with a slightly embarrassed laugh, like she should have thought of that herself. "I wish I had known how lonely you were sooner... Master candidate or not, I would have swooped down from on high and presented myself for your pleasure on the spot."

Isaac's chest bloomed with warmth at that. "Awww... That's really sweet of you to say, Princess."

"I mean it!" Luna insisted, clearly taking his compliment as him just humoring her. She started bouncing her giant ass on Isaac's crotch, her bubbly cheeks caressing the sides of his cock like the push and pull of the tides. "I know - mm! - what it's like to feel lonely, even surrounded by supportive - ah! - friends... Ah fuck, so big...!" Boing, clap, boing, clap! Her giant ass slammed down on his crotch over and over again, her deep crevice hugging and dragging up and down his cock. "Mm, I had - hss - half a mind to offer you a place in my bed after that first couple of meetings, to make up for - hngh - the bad news. Wouldn't have cared - hah - that your cock was smaller - nmm - or your stamina was lesser b-back then. I would have pleased you to exhaustion a-anyway...! But - mmmm - I didn't know if that would have... been too much pressure - ah - c-compounding the feeling of being stranded with no options in another world... Ahhhn~!" She was clearly enjoying feeling his cock rub deep between her cheeks, even as she gave him heartfelt reassurance.

Now Isaac knew that this wasn't true in the original timeline. He knew that the Princesses, and pretty much all the ponies he met, had had no interest in him sexually. Probably negative interest, actually, thanks to his odd alien pheromones pre-Root. But now, to think that in this timeline, one of the Princesses had been thinking of propositioning him a month ago...! "Nngh, I would've, Luna! I would've jumped at the chance to fuck you, then and there!"

"Then let's make! Up! For lost! Time!" Luna panted, punctuating each fragment of her speech with another booty-quaking slam onto Isaac's dick. "Cum, Isaac! Claim my ass! It's all yours! These mountains, cultivated for a thousand years, even every moment in exile; let your dick make itself home within! Spill a river between my Cutie Marks! Seed my valley with the proof of your virility, my noble knight! Mark this Princess, this guardian of the night, as your personal whooore~!!"

Under such **** on the senses, did he really have a chance of resisting?

Isaac gripped the bedsheets tightly and arched his back as his cock swelled and pulsed between Luna's massive, smooth cheeks. The evidence of him cumming wasn't even visible for a second thanks to how completely Luna's ass was covering his entire cock, but he could feel his cum pooling and smearing against the crack of her ass. Then spurts of white began to appear, **** out by the pressure before trailing down Luna's ginormous posterior, like magma oozing out of a tectonic crack in the earth.

Luna herself was also panting for breath. It had been next to impossible to see her hands past the wall of ass Isaac was beneath, but her shoulders were definitely turned inward so she could keep her fingers busy between her fat thighs.

A giant woman cumming just from an intense hotdogging... That thought tugged one more spurt of aftershock cum out of Isaac's dick.

He'd been right about it being the last one, though. Isaac's body felt drained - in an incredibly good way, but drained all the same. The spirit was oh so welling, but the flesh was spongey and... well, not bruised, thankfully (hopefully, with how heavy Luna's ass had been...).

A flash of blue magic swept over the both of them, cleaning up all the excess fluids between them. Luna then slowly got up, letting Isaac's dick drag out from between her cheeks and flop back onto his stomach. She giggled naughtily at the sight of him, a horny, tuckered-out little man. Then her horn ignited with a magical aura, lifting Isaac up towards the head of the bed, the covers opening up to accommodate him.

"It's time for me to watch over the night, my dear friend Isaac," Luna announced, walking over to the side of the bed with powerful strides and leaning down to give him a kiss on the forehead. "It is my duty to watch over and protect the dreams of my people. I'm sure Celestia will have big plans for you in the morning. For now, though, do me the favor of infusing my bed with your scent, so I may enjoy it long after you're gone~."

That was a favor Isaac was more than happy to perform. Before Luna left, though, he was suddenly curious about something she just said. "Wait... Um, now I'm thinking about if you looked into my dreams at any point..."

Walking to the balcony, Luna stopped and looked back over her shoulder. "I tried, but I did not find much success. You are not an inherently magical creature like the rest of us. Your dreams are purely biological. My unique magic turned out to be not entirely compatible, I'm afraid."

"Oh." Isaac thought for a moment as he pulled up Luna's moon-quilted covers up to his chin. "Well... Since the ambient magic of this world is slowly enhancing me in all the ways I noted earlier, maybe that means I'll be technically close enough to a magical being to see you in my dreams sometime soon?"

Isaac's body tingled all over for a moment. Luna gave him a sultry smile over her shoulder, her face framed by her starry mane and the moonlight shining through it. "I hope so, Isaac. I'm sure between the two of us we could concoct some lovely wet dreams together~..."

Her horn glowed, and she disappeared in a flash of teleportation, perhaps to someplace where she could monitor dreams in peace and privacy now that her bed was occupied.

As for Isaac... he snuggled up into Luna's pillows and passed out in minutes with a smile on his face.