Disclaimer: Naruto x Highschool DxD + Others (Secret for now) - I own neither
Thank you SINccubi for allowing me to use the Sinbi character for this story.
This is the story I hinted about in October, and I've been secretly working on the plot for it for months. After interviewing Sinccubi about their character, I'm finally confident about releasing chapters for this story.
Story Start!

Do you have any questions?

"Actually, I have a ton of questions... considering that I was brought here out of nowhere, and a portal opened up underneath my feet while I was watching some people fucking. My question, is where do I start to begin with my questions?"

A small boy held out a note as.

The boy himself was rather feminine in appearance, but with soft peach skin and bright blue eyes. He had several features that could belong to either gender, though looking near his hips and stomach would help one understand the leaning of his gender was more male. Of course, the silvery grey hair gave both a wise and slightly mischievious aura about him that didn't bode well for others. A small orange jacket with puffy sleeves, and black short shorts, as well as silver armor that covered little of his body.

Three whisker marks on each cheek as well.

"Well, for starters... what are you? No human I've ever met has so little... actually, you seem to have zero sexual desires... that's not normal for any species actually."

The grown woman who was speaking was tall, with a slightly burning skin color that looked like her skin itself contained the color of red. Her hair was a flaming red color and went well down beyond her back. There were no whites to her red eyes, instead it contained nothing but black, and with a seductive body that could put any pro prostitute to shame, her proportions were completely perfect in all aspects of them. She had a long devil tail sticking from her tail bone, and two horns shooting from her forehead.

She was a succubus, tried and true.

A completely master of the sexual arts, a being whose very life required feeding on those desires in order to survive.

Sinbi.

I am an alternate version of Naruto Uzumaki, who was created by the fusion of the Chakra of Naruto Uzumaki and the Magic of Eucliwood Hellscythe. My soul was formed when those two energies possessed the womb of a pregnant woman capable of holding these energies inside of her. Since the Chakra that formed me was larger than the magic, I inherited the Naruto name.

...

"You know, that raised a lot of questions. That answers more than I actually expected from that simple question... it seems we're somewhere... unconvenional for sure." Sinbi looked at the room around her. There were no doors or windows, there were zero entrances or exits, and there was a mighty magic that filled the walls of the room, completely cancelling out any forms of magical transportation in or out of the room itself. She couldn't use any of her magic to get out.

She needed to be calm and analytical.

I pulled you hear to offer you a deal.

"Oh, you want to make a deal with the devil, so to say."

No, a succubus is going to make a deal with me.

"Well, that is foreboding... you couldn't magic up some chairs, could you?" Sinbi asked with a curious glance around the room, for anything that could be used to sit on.

The next second, she wasn't standing.

She was sitting in a marvously red love seat, and her butt sank into it the perfect amount, with the seat possessing both perfect softness and firmness. It was like she herself was sitting on something designed to feel like she was touching a nice, firm rear end. She looked at Naruto, and she noticed that he was just pointing a finger at her.

"You control this world?"

My full name is Naruto Uzumaki, and my title is Silent King of the Underworld. In this Multi-verse, I'm something of a manager, I brought you here to make a deal for your benefit and the benefit of another.

"So that question went unanswered, and why me?"

You're a sexual expert, but unlike the usual slut succubus, you have a sense of honor and appreciate human freedom.

"Well, I'm flattered by the praise... though I do believe you called me a slut." Sinbu just smiled with a small teasing tone, hoping to get a reaction.

No reaction at all, and that took the teasing smile from her face, though it wasn't replaced with annoyance. It was simply no longer a teasing grin.

Yes, I did.

"Honest, so I was picked because while I'm still a 'slut succubus' I fit your more unique tastes. So, this deal? What do I get out of it?" Sinbi asked, before she was given a note. She read it over for a second, before she blinked. "That's... how..." Sinbi wasn't usually shocked.

The answer she got was both too shocking for even her to not react to it, but she was contained enough in her shock that her glasses simply fell down her nose a little as her eyes widened.

Naruto simply waved a hand.

"... How? No serious, you're saying that you can take a portion of my soul, and give it, it's own body. In this deal, I can exist in multiple places at the same time, with my... this is extremely complex magic I've never even heard of. I'm impressed such a young... no... you're ancient." Sinbi figured out his age after a few moments of paying attention. No Shota or Loli would have such a great emotional control, and neither of them would be so devoid of natural lewdness of curiousness.

This was an ancient being who had simply grown beyond a care for sex, and thus, was simply an ancient being.

He showed her a collar, that matched her hair color.

He gave her a note.

A new world is being created.
A foolish version of my originator, a human Naruto Uzumaki, is suffering from intense loneliness.
He's going to try to summon a devil to end his loneliness.

"... That's kind of sad, can I ask why-"

He will tell you himself one day if you accept the deal.

"I see, well, that is fair enough. If those are his secrets, I guess it only fits for him to be the one to tell me them. I'm interested though, this sounds like you're doing this out of the good of your heart... and what I'm getting out of this is too good... and what does that collar do?" Sinbi asked with a raised eyebrow. She wanted to know more about the deal, but she could feel some magic flowing into the collar.

Immortality.
Those that wear this collar are given eternal youth, are unable to die, and if their bodies are destroyed they simply respawn next to the person who is wearing the Master version of the collar.

"So, it's a contract. So, what exactly am I going to do?" Sinbi was only having her curiousity peaked by this new and interesting situation.

She felt like there was a catch to this deal, and she needed to find out what it was.

A book appeared in his hand.

He sat down in a chair, and flipped the collar around his finger. She saw the walls burn red as flaming words appeared on the white surface, and gave her his words for him.

He's a dense idiot, he's a natural hero who helps anyone he can, even at the cost of his own life. Your job, when he summons you, is to make a contract with him. Help him out where he needs it, he's a dense idiot, but he's good at attracting women to him. The more people that he loves and treasures, the stronger he becomes.
He needs a succubus who will help him, but not fall in love with him.
He needs a good familiar, and a teacher.

"Very well, I accept... I see no real downsides for me in this, and it seems like this will turn into a very lewd situation. He'll be surrounded by women, sounds like fun for me. I won't be expected to teach him to fight though, will I? I can't really do that." Sinbi stated to him, since she really didn't have that in her repetoire of skills.

Ask her to fuck a person to submission, but make them beg for more, and she could do that in a heartbeat. It was as simple as breathing for a being as lewd as she was.

Ask her to fight though, and she wasn't going to be able to offer much support.

With your help, he will seduce a teacher for himself.

"Master/Student fucking, that's hot, I appreciate that. Now, are there any downsides for me?"

Yes.

"What are they?" Sinbi asked curiously.

She blinked and got her answer.

She blinked, and she noticed that her body had changed into a much smaller version of itself. While she hadn't lost even a speck of her seductive charm. She noticed that her form felt lighter, different, weaker. Her powers had diminished as well, and reaching up, she felt she only had a single horn, and it was more curved, a lot smoother as well. Her glasses didn't fit her face correctly, and she looked down to see her clothes didn't fit. Her amazing breasts had shrunken down to a mere A-cup, and the rest of her had shrunken down as well. Her body felt tighter as well.

For your enjoyment.

"Well, this is no real downside, unlike others, I was never ashamed of myself when I was a petite loli, as a succubus, I understand the charm that a petite woman has. Anyway, I think I can enjoy the challenge this form gives me." Sinbi stated with a teasing smile back on her face. Her shrugged his shoulders, and she blew a little air out in mild annoyance at how unphased this guy was.

He gave her the collar.

This collar will lock you into that form, and when you are summoned, a mark will appear on him, marking him as the Master.

She gave it back to him.

"Before I get summoned... do you think I could test out this body some. It's been awhile since I was smaller, and I really want to remember what everything feels like before I go." Sinbi smiled pleasantly, and for the first time, she got a reaction out of him.

He raised his eyebrow.

Sure.

"Good, so, can you magic me a few toys so I can test myself. After all, it's not every day I can enjoy being this tight again."

You wish to masturbate.

"You want me to be in top condition, don't you? Well, getting used to this body is... well thank you for being so understanding." Sinbi found herself sitting on the floor, no longer on the couch, as she had an assortment of dildos of different shapes and sizes around her. She was going to get good use out of all of them. "You know, if you want, you can have fun with me." Sinbi offered him.

Sex was better than toys after all.

No, time moves slower in this realm.
Enjoy yourself all you wish, I'll inform you when you're about to be summoned.

Sinbi grabbed her first toy and licked her lips.

Time to see if she remembered all her sweat spots.

Chapter End!
Please Leave Me Lots of Nice Long Reviews, But No Flames Please!

If you want to see a picture of the final scene of this chapter, a link to a picture of it is on my profile.