The responsible way: By simmering down and negotiating.

Then Isaac took a deep breath and realized that there was a pit of nervousness in his chest. "Actually... How about we slow down and... talk this out?" It was the hardest thing in the world with the beautiful fashionista's lips practically drooling onto his cockhead, but this felt important.

Thankfully, Rarity seemed almost relieved at the suggestion, blinking and quietly snapping out of her submissive desperation. "O-Oh yes! Perhaps that would be best..." She got back up onto the chaise lounge and patted the spot next to her, inviting Isaac to sit.

Spike took note that things were slowing down and moved away from Isaac's cock. "Should I maybe... head over to Twilight's for now and let you two have a moment?"

Isaac felt weird kicking Spike out of the home of his crush - especially after being serviced so dutifully by him. "I don't really mind..."

"If our Master has no problem, then you're welcome to stay, Spikey-Wikey," Rarity cooed with a pleased smile.

Spike chuckled and put a hand to his chin. "Actually, now that I think about it, since I know you fucked Twilight, I should probably check on her. She's probably freaking out that there's a real Master candidate in town, and somebody ought to make sure she doesn't go into planning overload." He practically skipped towards the front door of Carousel Boutique, his booty jiggling all the way.

Rarity nodded. "Very well, thank you. Be a dear and put up the Closed sign on your way out, will you? I imagine I'll be... indisposed for a moment."

The young dragon almost cackled with naughty glee. The door jingled as he opened it, lingered as he put the sign up, and then finally, slowly closed after he had already started skipping gaily away. Which just left Isaac and Rarity alone in the Boutique.

Isaac finally took Rarity's offer to sit, his still-hard cock bobbing in front of him as he took a seat next to the half-nude fashionista. "So..."

"So," Rarity echoed, eyes locked on his cock. She reached over and gently stroked the top of the base of his dick in slow strokes, more petting it than anything. With how velvety smooth her hands were, it still felt electrically wonderful. "Have you never...? I suppose not, knowing you came from a more prudish world. I always imagined that, should the Master appear, they'd be already experienced in all the pleasures they want, but you're still learning, aren't you?"

Isaac chuckled sheepishly. "Yeah... Though now I'm wondering about you and whether you've... y'know, gone hardcore submissive with someone."

The fashionista blushed like she'd gotten caught. "...Mostly just read... literature on the subject. In preparation."

"Suppose that makes two of us," Isaac remarked with a chuckle.

An awkward pause reigned over the now quiet boutique for a moment.

After a while, Isaac finally decided to get things started again. "Okay, I'm down for trying out some more kinda BDSM-style domination. I have a greedy and selfish libido. I want to have willing, devoted sex slaves. I kinda want to objectify ponies and treat them like tools to get myself off."

Rarity shuddered in lust, her hyper-endowed hourglass figure jiggling top to bottom in her lingerie. Only sitting beside her did Isaac have a chance to appreciate how small her waist was, almost small enough to get halfway around with just his two hands. "That's good...!"

"Buuut," Isaac murmured, trying to be careful about his 'bad' news, "I'm also kind of a gentle soul. I don't want to make anyone actually unhappy, even if I'm going on a sexual rampage. I'm way too empathetic; I don't want to accidentally go to far and stomp all over your feelings. At the same time, I want to do what makes you happy too, and if being a dominant, greedy, selfish kinda jerk is what you like best, I want to try and accommodate."

"So... are you thinking we use safewords, signals, personae, the whole nine yards?" Rarity asked after a second to process.

"I think a safeword would be a good start, yeah," Isaac agreed, in mild disbelief that he was establishing such boundaries with a half-naked anthropomorphic pony. "And I also just kinda want to get a sense of... what you're looking for from this. How you want me to act, how far to take it. I think this'll work best for me if I can have an 'On' and 'Off' mode, just so I can kinda feel safe, I guess."

Rarity nodded in thought, staring off into space as she idly continued stroking Isaac's dick. "I think I'd like that, too. I'm still craving that utter domination, that risk, but knowing that I set the terms brings me some... realistic comfort that was always missing from my fantasies, I suppose." After another moment's thought, she added, "I think my safeword might be prêt-à-porter."

"Prêt-à-porter, got it," Isaac repeated with a chuckle. Of course it would be something fashion-themed. "And that means 'hold up, something about this is wigging me out, let's work through this.'"

"Perhaps..." Rarity paused for a moment, then looked away from Isaac's cock and into his eyes. "Truth be told, I get this feeling this is all more for your sake rather than mine. I'm not sure there's anything I would ever deny you, Isaac. You could slap me across the face with this club of a cock and I would thank you for gracing me with your attention. You could walk over to that rack over there and tear every dress apart with your bare hands if it got your rocks off."

Isaac blinked in astonished surprise. "That's... Whoa." And she was totally on the mark about who all these safety tools were really for...

Rarity turned a little more towards him and put her hands on his bare chest. "I don't want to be in the slightest bit of control. I want a Master I can give myself to, completely and utterly, damn the consequences, not another thought in my head. I don't want or need a cruel or aggressive Master. Just one who knows exactly what he has and is willing to use his property to the fullest."

Suddenly this had all gotten turned around on him - the fashionista was downright seducing him with her big sparkling eyes and tender touches. "I... But... We've barely just met... How can you trust me...?"

"Oh, darling~... I'm not one to believe in predestination or fate, but... the moment I saw this massive cock in my face" - which she emphasized by laying one hand atop it again - "I knew it in my heart as surely as I know the sun will rise: You're the one. The Master we've all been waiting for...! No other male could possibly own me so utterly just by waving his cock in my face! Call it love at first suck~."

And that's when everything fell into place for Isaac. This was Rarity the hopeless romantic, perverted and converted into Rarity the helpless submissive by all of his reality changes. The passion she invested into her canonical romantic fixations had now all been reallocated into submissive passion for the hypothetical Master! It was crazy and reckless... but so was 'true love at first sight.'

Rarity leaned in closer, draping her arms over his shoulders and pressing her bust against his chest, smooshing her breasts against him until they were covering up to his neck and down to his stomach. "So yes, I'll do everything I can to make you comfortable, Master, to reassure you that I do want whatever you have in mind for me, whatever it may be. If you want to set up some ground rules to protect you from 'top drop,' I'll follow along gladly. Or if you just want me to say 'thank you' after you call me names, grope my body, and leave me a cum-stained mess on the floor, I'll do that too~."

Bizarrely, Isaac found himself wishing that Spike had stayed behind a little longer. He felt like he was in the lioness's den without any backup.

Man, I've got some complex hangups about gender roles and sex, Isaac internally realized.