Winning over the Princess of the Moon.

Princess Luna's bedchambers were subtly different from Celestia's. They had the same layout, but where Celestia's private quarters looked like she hosted parties and orgies with room to spare, Luna's room and its furnishings had the telltale spacing of someone who just liked having a lot of open space to themselves. Most of her furniture and personal affects were up against the walls, giving the space around her bed lots of room to walk around.

Then again, with an ass as gargantuan as Luna's, maybe keeping things clear at hip-level was just sensible.

"So, what'll it be, 'Master'?" Luna asked provocatively, magically closing the balcony doors behind Isaac once he entered. "Or would you make your humble servant take the lead for you?"

Everything up to this point gave Isaac a pretty clear sense that Luna especially did not want to take the lead. She wanted someone who would boss her around, tell her what to do, and say it confidently. Admittedly not something Isaac was used to doing in the bedroom - among just about everything else due to his inexperience - but fucking all of Celestia's holes and hearing her praise had given him a lot of fresh confidence to go experimenting with! So he thought quickly and said, "How about we get more acquainted..."

Luna furrowed her brow. "I do have duties to attend to later, so I'm afraid taking it slow is not-"

"...and by 'we,' I mean you and my cock," Isaac finished, jumping onto the edge of Luna's bed and spreading his legs. Her bread, like Celestia's, was surprisingly tall and sturdy, making him feel rather small compared to the lunar Princess, but he soldiered through the feeling regardless.

Thankfully, Luna was appreciative of his little gag. "Aha! I see! Yes, I suppose I should get to know the tool that will attempt to claim my full moons." She dropped down to her knees, her thighs squishing together and her ass quaking behind her, making Isaac bite his lower lip automatically. The regal Princess leaned in, her starry mane flowing like water over Isaac's thighs. Isaac's cock was most of the way hard, only hindered by adrenaline and Celestia draining it mere minutes ago. Luna took a deep sniff of his musk and pheromones, then let out a shuddering gasp, closing her eyes to savor the scent. "Ohhh, this is... quite unusual. More... potent than any other male I've encountered... Mm, I can still smell Celestia's fragrance on you..." She leaned in to give his shaft a quick lick with the tip of her broad tongue. "Taste her drool on you, too...!"

"Is knowing that I recently fucked someone else super-hot to you creatures?" Isaac asked with a knowing grin.

"As if you need to ask at this point," Luna scoffed playfully. She leaned in some more and let his cock rest directly on her muzzle, between her nostrils, her eyes crossing slightly to focus on the shaft as it stood erect above her forehead. For a moment, it was like her whole world was Isaac's dick, and that thought made him throb. Then she slid further down and pressed her mouth against his balls, alternating between gentle kisses and lightly sucking on the sensitive flesh with her lips.

Isaac quite liked the attention she was giving him down there, so on a whim he decided to give her a bit more of an incentive. "Ahh, you're a bit of a ball-slut, aren'tcha?"

Luna's oral appreciation grew more intense and direct. She actually adjusted her posture, kneeling wider so she could lean lower and get her mouth around one of his enlarged balls to suck into her mouth, savoring the feeling of it filling her lips and lashing it with her tongue every which way. Then she released his left ball with a 'pop' and immediately lavished the same treatment on his right ball, her eyes rolling up slightly as she indulged herself in pure ball worship.

Isaac leaned back on the bed, a wide grin on his face as he appreciated the situation. At the start of the day, he was wandering through a cave because he felt ostracized by the ponies he was stuck with. Now, at the end of the day, he was laying on a Princess's bed with said Princess fervently between his legs to suck on his balls like they were the last drops of water in a drying oasis.

And to think, this was only the beginning...!

Luna gasped and finally came up for air, switching gears and rubbing his cock all over her face. "So male, so virile... Truly, none others even compare. Why couldn't you have landed in our world sooner? When we convened a month ago to try and send you home, why did you not just whip this out right then and there and claim us?"

Oh, right. They had technically met once before, even in this drastically changed timeline. Thankfully, there was already an explanation that kept things relatively tidy. "Well..." It was getting a little hard to put words together with how much Luna was rubbing, kissing, and licking his cock! "Truth be told, I arrived much more humble. I've been steadily growing over the last month."

Luna paused, her big bright cyan eyes wide in shock. "You mean... you have grown to this lustrous size? Are... Are you still growing...?"

Isaac grinned. "Far as I can tell, yeah. That makes it even hotter, right?"

That elicited a groan of pure need from the Princess. She pushed forward, tilting his cock back until it was nearly lying against Isaac's stomach as she familiarized herself with every fold and vein. "Fuck, which means... you're only going to get bigger, and bigger, and bigger...! Soon even the mightiest dragons will bow before your phallic superiority...! You'll have dozens of sluts crowding around just to lick a mere fraction of your godlike cock~...!"

Then, out of nowhere, she jerked away, turning aside and leaving his cock twitching in vain for more stimulation and praise.

"I-I can't..." Luna whimpered, her face a mask of sorrow. She took a deep breath to steel herself, then explained, "Long story short: I... was one of the unfortunate mares who rushed into being Branded by Rockhoof, the first Harem Master candidate. My sister did not. And among other things, the pain of that loss... contributed to me becoming Nightmare Moon and then being banished to the moon for a thousand years."

"Oh." Isaac had gotten a brief primer on the broad strokes of Equestrian history, thanks to Twilight, but the timeline now had some significant changes thanks to the ripple effects from his questions. Still, his dick was throbbing with need and that compelled him to help her get through this. "Well, I think, uh... If Rockhoof were here, he'd want you to keep up hope and devote yourself to the true Harem Master with gusto, right? Heck, he'd probably be worshiping my cock right next to you, right?"

Luna actually chuckled at that, wiping some moisture from her eyes as she stared off into nowhere. "Indeed he would... But no, the issue's not Rockhoof. Truth be told, I have no ill will towards him, but also no lingering attraction. He tried his best, but once it was over, it was over." The lunar Princess let out another shuddering sigh. "I was just... mad because I felt like Celestia had known something I didn't, and set me up. And now... even though everything in my body is screaming at me to descend into the spiral of lust and serve you, I can't... I can't rush into it again, no matter how perfect of a candidate you seem to be. My sincerest apologies, Isaac."

Oh, that was a misread on Isaac's part. Well, those reality changes were still potentially fun.

Isaac thought for a moment about how to address the issue. He didn't want to necessarily just ask a question that made Luna instantly get over it - not that he was above just changing ponies' personalities, since he'd already overwritten plenty of hearts and minds so far. But removing obstacles to his universal comfort and success was one thing, while just editing the little things that made people unique until they couldn't bother him was quite another.

...Besides, Isaac kind of liked this emotional drama.

In a moment of empathy and insight, Isaac realized that the solution didn't really even need the Root of Honesty at all. "Well, then... Let's put aside the whole Harem Master thing for now. For tonight, we're just two adults who wanna fuck."

Luna finally looked back at him in genuine shock. "T-Truly...? You don't... need me to stand on ceremony...?"

"Luna...!" Isaac rolled off the bed and stood before her with one hand on the base of his cock, keeping it nice and turgid as he waved it in front of her. "I'm horny and want to fuck. You're pent-up and wanna fuck. We don't need any Harem Master tradition to resolve that. And if we wanna fuck again later, we'll just fuck again later. If we catch feelings for each other, we'll cross that bridge when we come to it. But for now, this is just casual sex."

The Princess glanced down at his waving cock, her eyes tracking its movements hungrily. "But... we're predisposed to need a Master... We should find out as soon as possible whether you're the one or not..."

"That's gonna take some time, and I'm still 'growing' into my role," Isaac asserted with a chuckle. Feeling bold, he reached up and ran his hand along Luna's muzzle. She instinctively buried her nostrils in his palm and took a deep whiff of his natural scent. "There's times for worrying about what the future holds, and there's times to live in the present and take what joy you can with what you've got. No sense worrying about the thousand things that could happen." Then Isaac turned away and coughed, chuckling with a rasp. "Sorry, I'm extremely throwing stones from inside my glass house, because I'm a huge hypocritical worrywart who gets hung up on things like word choice. But you get my meaning."

Luna giggled with him, her eyes shimmering with hopeful joy. "You... You truly don't need me to call you 'Master' or anything? You really just... want to fuck me tonight?"

"Luna, I wanted to fuck you from the moment I first saw you," Isaac replied with complete honesty. Even before all of his 'enhancements' to the women of this world, the Princesses had been equally imposing and beautiful. He'd come here first with his cheat power for a reason! "I just had a lot of baggage from back home telling me I wasn't worthy of you, any of you. But not anymore. The Master stuff is nice, but honestly, I just wanna fuck all of you to my heart's content, damn the consequences."

She reacted like he'd said the most romantic words any pony could hope to hear. "Isaac~!" The tall alicorn Princess wrapped her arms around him and scooped him up like he was a mere teenager. She stood up, hefting up his adult human body like it was nothing, carrying him more than his full height off the ground. Thankfully, the ceilings of the castle had more than enough head-room for the insanely tall alicorns.

Holding him up by his bare ass, Luna pulled Isaac's crotch to her face, swallowed his cock down to the hilt in one smooth slide, and proceeded to suck his dick like a drinking straw, hard and fast. It was all Isaac could do to hold onto her horn for stability, completely powerless to do anything but feed Luna the cum she so desperately craved, that his balls had dutifully churned up for her.

What really got Isaac, though, was the look on Luna's face with her lips sealed around his cock. She looked... incredibly happy. Her eyes were shut, tears of joy were leaking down her puffed cheeks, and the corners of her muzzle were curled upwards in a smile that couldn't be **** back down. It was like just letting go and sucking his cock like a succubus out of hell had solved all of her problems. It was a powerfully emotional and arousing sight, an effect Isaac never assumed he'd ever have on a woman.

After being worshiped and teased and temporarily blue-balled, Isaac couldn't withstand it any more. With a loud groan, his cock erupted straight into the back of Luna's throat. She anticipated each pulse with practiced ease and started swallowing at the perfect time, gulping down even his enhanced pint-full loads.

Then she did something Isaac wasn't expecting: She slowly pulled him out of her mouth, dragging her lips along his shaft, making him twitch with pleasure. His cock popped out while he was still cumming, spraying obscene amount of semen all over her face, her mane, and onto her neck and breasts. Her black crown and collar became stained with white. Her starry mane gained a few milky-white nebulas floating in their magical, wavy fields. And Luna just basked in the shower of his cum, turning her head side-to-side to make sure both sides of her face got a healthy coating.

Isaac's stiffness finally released and he fell limp in Luna's hands, panting for breath. After fucking Celestia all afternoon and now Luna, his cock was starting to feel a bit of soreness. His stamina might have enjoyed a month of gradual magical enhancement, but it was still limited, and he was starting to hit that limit.

Luna licked her cum-stained lips, enjoying the flavor of his cum on her tongue. "Mmm~... Any other stallion would have fucked me because they saw it as their duty, giving me the gift of being my temporary Master. But fucking just because you want to fuck? Isaac..." She leaned in, her eyes sparkling with naughty delight. "You're going to be very popular around here~."