Author's Note: Once again, a bit shorter than a normal chapter, but I'm still writing my novel. Still, it's about as long as the last two chapters put together, so I'm getting my groove back. And yes, there will be another chapter in two weeks.

"Uhhh...," Naruto said, looking up at the Fox that towered over him like a colossus over an ant.

Kurama stretched thoroughly, arching his back up before leaning forward and then back. The snaps and crackles of popping joints sounded like exploding tags.

"Ahhhhh," Kurama said. He trotted forward, loping around the perimeter of the immense room. He stretched out, moving faster and faster until he was a blur of red light zooming past Naruto multiple times a second. Naruto stared, mouth hanging open in shock, as the Fox stretched his legs for the first time in decades, if not centuries.

Eventually the bijuu slowed down, dropping from a run to a trot and back to a walk. Finally he stopped and shook himself again before climbing up on the pillar atop which Naruto always appeared when he entered the mindscape. He turned in a circle three times and lay down, nose-to-tails, his glowing black eyes locked on the jinchuuriki far below.

"It's interesting how satisfying this is," the Fox said casually. "The net prevented me from getting up here, or using my abilities in the space above the pedestal. There's nothing particularly special about this spot—it's not more comfortable than the rest of the room, and certainly not more spacious—yet I have to admit that it came to seem very appealing, simply because I was denied access. It's quite pleasing to finally be up here." He turned on his back and wriggled a bit, feet and tails in the air as he got comfortable.

"So...," Naruto said. "What...uh..."

"What happened? What did you do? What happens now?" Kurama asked, curling up comfortably.

"Uh...yeah," Naruto said. "Those."

"What happened is that you damaged the seal that confines me," Kurama said. "Which was nice of you. Stupid and poorly thought out, but nice."

"So...if you're free, why are you still here?" Naruto asked cautiously.

"Oh, I'm not actually free," Kurama said. "The physical seal, the one on your stomach, is still largely intact, so I can't leave your mindscape. No, what you just destroyed was the inner seal, the one that bound my ability to use power here. It's still your mindscape, but attempting to pin me to the floor again or otherwise control me...well, let's just say that it would be something you should think long and hard before trying."

He shifted again; the surface texture and shape of the pedestal obligingly changed themselves to provide the vast creature greater comfort.

"Now, without the inner seal, I'm not confined to this room anymore," he said casually. "I can wander freely through your mindscape, stretch my legs a bit, maybe find some more comfortable and interesting surroundings. I'm sure you have some fields or mountains around here somewhere."

"That...sounds dangerous," Naruto said carefully.

The Fox flicked a tail dismissively. "Oh, don't worry, I'll be fine," he said. "There's nothing in here that can hurt me. I mean, I suppose if you really wanted to turn it into a straight fight it could be a bit tricky...it is, after all, your mindscape, not mine. Still, I don't see any reason why we should fight, do you?" Two firey eyes the size of dinner chargers stared unblinkingly down at the very young, very nervous genin.

"No...?" Naruto said.

"Excellent," the Fox said expansively. "I'm so glad we had this chat. Now, I'd like to have a nap, so you should feel free to head back." He lay his head down and allowed his eyes to fall closed, giving a final small wriggle as he settled in.

Naruto swallowed. "But...I still need to borrow your chakra so we can save those people," he said carefully.

"Nope," Kurama said, not opening his eyes.

"But, they'll die!" Naruto said.

"We had this conversation," the Fox said, still not moving. "Which part of 'no' was unclear? Leaving aside all the other issues, you physically aren't capable of it. Shielding yourself from the fire is one thing; you could probably manage that for a short time. Shielding yourself and a large group of others while walking through a firestorm, into and out of buildings, and up stairs? No way. I have no interest in going back to Hell, thank you."

"Please?" Naruto asked.

For a moment the Fox lay still. Then he sighed and rolled up onto his haunches. The ground under Naruto rose up, making the genin stagger in surprise as he was lifted to Kurama's eye level.

"You really want to save these people?" the Fox said.

"Yes!" Naruto cried.

"Fine," the Fox said. "You'll need to give me temporary control of your body so that I can manage the flows myself."

"Uh," Naruto said. "That...um...sounds bad."

The Fox shrugged. "Personally, I don't give a damn about those people," he said. "This entire city is the kind of disgusting hellhole that my brethren and I would normally demolish, and I'm happy to let them burn. But, it's important to you. So, fine, I'll help. But I want something in return."

"What's that?" Naruto asked cautiously.

"Full sensorium access," Kurama said. "This window is better than nothing, but it's tiny and it's limited to your puny little senses. If I'm going to do a major favor for you, I'm going to want something better. While I'm in control, I'll do some basic remodelling to make your senses work properly—you'll get enhanced vision, smell, touch sensitivity, etc. I'll also be able to use my own senses through you, although you don't have the brain structures to understand that information so I'll route it around you and just pipe it down here. I'll also do some physical work while I'm at it; changes to your musculature to grant improved strength, speed, and reaction times—that sort of thing. Last thing I need is for you to end up dead and me back in Hell, so it behooves me to do everything I can to prevent that."

"That sounds very risky," Naruto said. "How would it even work?"

The Fox shrugged. "Think of it like a permanent physical henge. I'll be reshaping your gross physical structures, and also reprogramming your DNA so the changes will become your body's new baseline form. That way they'll persist across your own henges, kawarimis, and so on. It's more subtle than a human could pull off, but I'm the Nine-Tails. I've had billions of years to get good at this." He paused, eyeing Naruto carefully. "It'll benefit you as well, of course," he said. "Just think how useful enhanced senses and a stronger, faster body will be in your line of work."

"How do I know I can trust you?" Naruto asked.

Kurama looked at him in disgust. "You rude little monkey," he growled. "When have I ever proven untrustworthy? I have been ridiculously helpful since you showed up. I helped you against your teacher when she was hurting Hinata—do you think you could have stopped Anko on your own? No! I protected your vixen. I told you to talk to her when you were making a thorough mess of your relationship! I taught you how to control your mindscape! I told you about your parents when no one else would! I offered you the Rasengan when I didn't have to! I did all that, gave you all that, freely and without any price, and you have the gall to question my trustworthiness?! What do you think I am, you obnoxious little meatbag—some lying bastard human? I'm a bijuu! Unlike you stinking apes, we keep our promises. We can't not, it's part of our fundamental nature. Don't you ever question my integrity like that!"

The Fox glared down at Naruto, his jaws clenched tightly together and the fires in his eyes whirling furiously. All nine tails slashed furiously back and forth. "In fact, screw you," Kurama growled. "You question my integrity? Fine. You can go to Hell, and I hope you can hear it as those people burn." He flopped down again, putting his back to Naruto.

"No, please, I'm sorry!" Naruto said desperately. "It's a deal! You can have it, full sensorium access, whatever. Just help me!"

For a long moment Kurama said nothing. Finally, he uncoiled and turned back to Naruto, looming over him like a judge staring down.

"The seal requires that the bargain be clear and willingly entered," the Fox said. "You will grant me control of your body, the right to upgrade your body and fix your ridiculously limited senses, and permanent access to your full sensorium, as well as my own senses which you will not have access to. In exchange I will do everything in my power to rescue whatever civilians the Sound nin named Hideo guides us to and ensure that they emerge safely from the firestorm. Do we have a bargain?"

"And you promise not to hurt anyone?" Naruto said.

Kurama growled. "Fine," he said. "But I'm not rendering myself unable to fight back if attacked. I promise that I will not deliberately harm any human who does not pose a clear and present danger to me or to you, with the understanding that 'danger' shall include imprisonment, application of additional seals, and other non-physical harms."

"Okay," Naruto said. "That's fair. I ag—"

He paused. Memories of his team came to mind, all carrying words of warning.

Anko: You've got a good brain when you remember to use it, but you don't remember to use it.

Shino: The Fox is clearly an excellent weapon, but it is a kunai with a sharpened handle. Avoid it.

Hinata: Don't ever do that! It could have killed you.

The weight of what he was about to do finally started sinking in. He was dealing with a bijuu...and not just any bijuu. This was the Nine-Tails, the most powerful creature in existence, a being out of legend who was undoubtedly smarter than Naruto himself.

"Say the bargain again?" Naruto asked.

The Fox frowned, but repeated the bargain, adding the clause about not harming anyone.

Naruto thought carefully. During their recent downtime, Anko had had Shino teaching them some of the rationality techniques of his clan. One of those techniques was called 'Murphy no jutsu', and it centered around anticipating and preventing problems; if there was ever a time for it, that time was now. It was a simple technique—no hand seals, no chakra, just a special way of thinking: imagining failure modes for a course of action and how they might come about, then finding ways to prevent those failures. The way to do that was also simple: figure out how you would cause those failures if you wanted to.

Okay, what was the worst case that might result from this bargain? Easy: Kurama running rampant, causing destruction and chaos.

If Naruto were in the Fox's place and wanted to escape from the seal, how would he do it? He'd need to damage or destroy the seal...which he could do, if he had control of the body. A knife to the stomach that broke the lines of the seal would probably work. Alternatively, he could allow the fire to burn Naruto, again damaging and obscuring the seal. Would that actually work? A seal was a metaphysical thing as much as it was physical, an arrangement of chakra tethered to the real world by a design. Maybe the chakra imbued into it would prevent the design from being damaged? Or maybe damaging the design was irrelevant—maybe the physical design was needed only to set the chakra pattern and afterwards it became irrelevant. Naruto simply didn't know enough about sealing to be sure one way or the other. Still, assume that physical damage would disrupt the seal; as Shino had said, be as pessimistic as possible. After all, if he was wrong then no harm was done.

Was that true, though? Kurama's help was critical, both now and in the future. Right now they had a working, albeit occasionally abrasive, relationship. It seemed like maybe they were starting to be something like friends. If Kurama really was playing straight with him, then showing too much distrust could damage that relationship.

No, it was worth worrying. Shino had repeatedly emphasized the 'planning fallacy', the fancy Aburame name for the simple idea that most people instinctively assumed the best case outcome, even when they were trying not to. He'd trotted out an example about when his cousin Hideko had gone through the Academy; an instructor had asked thirty-seven of the students to estimate how long it would take them to learn the henge jutsu "if everything went as well as it possibly could"; the average estimate had been 27.4 days. They had also been asked to make a conservative estimate; the average had been 33.9 days.

The average actual time to learn to henge had been 55.5 days. 70% of the students had gone past their estimates.

It is very difficult to make your predictions and estimates be more pessimistic than reality, Shino had said. This was a time to be pessimistic; if Kurama was on the level then any insult or distrust could eventually be made up for. If he wasn't, then the consequences of too much trust would be catastrophic.

The problem, of course, was that Kurama was definitely smarter than he was.

"Well?" the Fox growled. "Tick tock, there's people burning while you sit here."

Naruto grimaced. "I'm really sorry about this," Naruto said, biting his lip. "I'm just worried about doing something stupid. You said you would like to destroy Sound, and I don't want that to happen, so I need to make sure I don't make a bad bargain."

The Fox gave an exasperated growl. "Boy, what I want is to not be peeking out through a tiny little keyhole, and to make sure you don't end up dead and me consigned to Hell. I've already promised not to gratuitously hurt anyone but fine, I promise I won't destroy this pustulent little hellhole. We may have to knock over a building or two to get your people out, but I'll keep the damage to a minimum."

Naruto licked his lips. "Promise me one more thing," he said. "Promise that you will obey the spirit of the bargain as well as the letter."

Kurama frowned. "No," he said. "I am a bijuu; I am physically incapable of deliberately breaking an oath, and the consequences for accidentally breaking one are painful. I'm not going to agree to be bound by something nebulous and undefined where I could end up suffering because you and I had different understandings of what part of the oath meant. If you want something specific, ask for it. I'm willing to be reasonable."

"What I want is to save these people with the minimum amount of harm caused to everyone and everything, and no harm at all to my precious people," Naruto said. "Also, to make sure that after we rescue them I'm back in control of my body and mind, and you're still here inside me. Will you promise me that?"

Kurama considered the request. "You're not exactly trusting, are you?" he asked grumpily. "Honestly, what cause have I given you to be so doubtful of me?"

"Well, you did lie to me," Naruto said.

Kurama sighed. "Once," he said. "As a test. And I told you afterwards, even though I didn't have to, and I explained why I'd done it. But, fine. In the interest of allaying your suspicions, I'll swear. Here are the terms of my oath:

"I will do everything in my power to rescue whatever civilians the Sound-nin named Hideo guides us to and ensure that they emerge safely from the firestorm as quickly as possible. I won't spend more than twenty-four hours on this task—I refuse to be trapped into being a permanent rescue team. During the period of this rescue effort I will not deliberately harm any human who does not pose a clear and present danger to me or to you, with the understanding that 'danger' shall include imprisonment, application of additional seals, and other non-physical harms, the precise list of which are at my discretion. I will also cause the minimum possible amount of property damage compliant with effecting the rescue. Once the rescue has been effected I will relinquish control of your body and return to your mindscape. In exchange for that rather paranoid list of strictures, you will grant me the following: control of your body for purpose of the rescue; permission to permanently upgrade your body so as to improve your senses and boost your survivability; permission to install my own bijuu senses; permanent access to your full sensorium. You understand that you won't have direct access to my bijuu senses since you lack the requisite brain structures. Now do we have a bargain?"

Naruto tried to look for any other loopholes, but it seemed pretty tight. He had a feeling that he wasn't doing the Murphy no jutsu properly, that he should spend more time thinking, but time was limited. Those people were in danger now, and every moment that he spent haggling was another moment that they could be dying.

"Okay," he said. "We have a bargain."

The Fox's jaw dropped open in a vulpine grin. "Eeeexcellent," he purred, expanding upwards and outwards even as he thinned into smoke that boiled away through the ceiling.

Naruto looked around dejectedly at the immense empty room, then made himself a bridge so that he could cross over to his original pillar and sit down in front of the window.

o-o-o-o

"Naruto?" Anko said carefully, shaking his shoulder. "Naruto? Can you hear me?"

Naruto eyes popped open, burning like the embers of Hellfire.

"Naruto's not available at the moment," the Fox said. "May I take a message?"

Anko's eyes widened and she stepped back, her face going pale. "Oh crap," she murmured, unconsciously scooping Hinata and Shino behind her.

The Fox watched her from behind Naruto's sapphire-blue eyes, his mouth dropping open in a grin that bared an entire mouthful of square white teeth. "Don't worry," he said eventually. "I'll be good. I promised him I wouldn't hurt anyone who wasn't trying to hurt us...and you're not trying to hurt us, are you Anko-sensei?"

"No," she said carefully.

"Excellent," said that demonic voice. Naruto's body rose to its feet with an inhuman smoothness, then twisted and turned as the wearer examined it critically.

"My, my, this is worse than I thought," the Fox said to itself. "Scar tissue on the lungs from where that shrew stabbed him, more scar tissue in the stomach from the bleach, malnutrition and vitamin deficiencies...someone seriously needs to teach that idiot child that ramen is NOT a food group." He sighed theatrically. "Well, to work, I suppose."

"Forgive me, Fox-sama," Hinata said hesitantly. "Is Naruto-kun all right?"

"Hmm?" said the Fox, looking up. "Oh, it's you. Yes, he's fine. He's not able to do the chakra manipulations necessary to get into the fire and out with all of you, so we made a bargain: I get to drive for a time and I rescue the idiots for him. Now, if you'll excuse me, I need to rewrite every aspect of your boyfriend's body right down to the genetic level."

Red chakra boiled out of Naruto's body, so hot and so dense that it completely obscured him from sight in a vortex of crimson fire. A wind sprang up, rising quickly to a shrieking gale as the vortex sucked in air and tore it into its component atoms. Hideo and Team Anko stepped back, hearts in their throats as they waited to see what would be left of the young genin at the heart of the maelstrom.

Author's Footnote: In the /r/rational thread for chapter 23, Reddit user 'Gnimhey' wrote: To be fair, a fair amount of chakra was probably going into "RAMEN IS NOT A FOOD GROUP, IDIOT CHILD, AM I REDUCED TO CORRECTING THE POOR DIETARY CHOICES OF MALNOURISHED ORPHANS NOW?" It made me laugh so hard I needed to use it.

'Murphy no jutsu' is a real thing that you can really do in the real world. Read the Wikipedia article on 'planning fallacy' (and maybe some of the other literature). If there's only one thing you're going to take from the rationality corpus, the planning fallacy is arguably the most useful. You will spend a large part of your life making plans and estimating how long they will take to complete. Being wrong on those plans has a high cost; understanding the literature can help you make better estimates, which is one of the most useful life skills available.

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