Hiruzen led Dix inside from the cold and they walked together to the Hokage's Office in silence. Upon entering the Third moved straight to one of the cabinets, opened it, and pulled a huge sealed scroll out of it. It had the words 'Forbidden' written on it. He then proceeded to take it to his office desk and laid it out on it. Dix followed him and sat down when he was invited to do so. Hiruzen handed him the scroll, opened at where the technique he needed was recorded. He also summoned a smaller scroll and picked up one of the pens from his desk and handed them both over to Dix.
"Here, you can copy the part and take it away. Keep it very safe, as this is an extremely strong and rare jutsu, so don't you dare come to me saying you lost it! Also if you ever manage to learn it or memorize it to the point you don't need the description anymore, burn it as soon as possible, so the technique doesn't get into wrong hands. Above all, this technique is forbidden for a reason. Make absolutely sure you are not in danger while you practice it. Do not try to rush it, your safety is way more important."
Dix listened to the Third's many advice attentively and memorized all of them. He can't take this lightly, as a major mistake could cost him dearly. He copied the technique fast, then handed the scroll back over to Hiruzen who stood up to put it back to its place. Just writing it down took almost 5 minutes, there were so many descriptions, depictions and warnings! The technique took up a good chunk of the forbidden scroll, and almost filled the entirety of the small one Dix was given.
"Naruto, you have to make absolutely sure that both you and the scroll are safe at all times! Don't cut corners and do your best. I believe in you." Hiruzen said as he returned from the cabinet, while looking straight into Dix's eyes with a very serious face.
"Yes, Uncle Hiruzen, thank you, but also, don't worry. I will make sure to do as you said." came the answer in a respectful manner. At this Hiruzen nodded and cracked a small smile.
"Go on now. I know you are eager to begin studying the technique. Come back regularly to tell me how you progress. Good luck, Naruto!"
"Thank you, Uncle Hiruzen! I will be going now..." he said and left the door, and soon the building. Hiruzen just sat back into his chair and leaned back with a dreamy face. He couldn't wait to see how far that young one will be able to go.
Dix rushed back to his house, as it was getting quite late, so he didn't go out to the woods just yet. He entered his house, threw his boots off, then quickly sat down to his table so he can start learning the technique as fast as possible. As said, it was really long, and even though he could've memorized it all, he didn't trust himself enough to flawlessly remember everything, so he intended to keep the scroll.
The technique wasn't only a long read though, but it was a monstrous task to actually learn and execute. The major steps are few in number, but the actual way of getting them to work are really hard and complicated.
The first thing to understand is that this is a space-time ninjutsu, meaning its quite unconventional compared to any other jutsu. These techniques tap into other dimensions to use as a means of transportation. And getting to other dimensions is simply... hard. Dix will have to feel things with his chakra that isn't really there. Or something like that.
Dix first thought he will be able to use Minato's advancements in this matter, for example his formulas, but there is a strange rule that is at work with these dimensions. Every person has their own dimension or set of dimensions their chakra is attuned with. Its also theorized that when someone first uses their space-time jutsu a new dimension is created to accommodate the breach in space and will stay there for the user to keep, but nobody actually knows. Everyone's chakra moves easier towards their specific dimensions, while trying to access someone else's is way harder. Obviously its possible, but its something monsters like the real Madara can do, and not many others. All this concludes that Dix has to start from scratch, doing his own research and finding his own dimension.
This is actually a bit better, as if he has access to his own personal dimension he could store stuff there or hide there if needs be. This needs its own research though, as the Flying Thunder God Technique is heavily focused on rapid traversal between these dimensions, thus Dix will have to build upon it to properly access it.
The first step on the long list of instructions is creating one's own 'formula'. This is the thing that was always seen in the anime being placed wherever Minato went. It is the mark where upon executing the jutsu the user will land at. It is basically a space-time homing beacon. It is heavily infused by the user's chakra, thus its able to emit a signal that will lead the user to itself trough the dimensional void.
Dix had a hard time wrapping his head around what was written in the scroll. He really liked experimental physics in his previous life, but there humans barely touched the surface of the concept of multiple dimensions and universes and such. This one is the real shit though. The inner scientist awakened in him, demanding experiments to find answers. He was really excited at all the thoughts that popped into his mind, but he shook his head and focused back on the task on hand. Maybe later, this is more important.
The next part was to summon himself into his own dimension, which includes first finding it, which is quite hard itself. This part contained the most description, tips & tricks and warnings of all. For example the user had to make sure there is a working formula already placed down somewhere, because without that the user might get stuck in his own dimension, as there is nothing to lock onto in the real world, thus return becomes almost impossible. Dix started to understand why this technique was forbidden.
The last step would be probably the easiest, when the user is already in the dimensional void and locks onto the chakra of the formula, and does the same as getting there in the first place, but with a clear destination set this time. The exact way to move between dimensions is something like a summoning jutsu, but is a modified version of it, that lets the user summon itself to the formula extremely fast, but it also is only possible while inside the dimensional void. That is why entering there first is needed.
By the time Dix got all of this shit into his brain it was already late in the night, so he went to sleep to continue the next day with a fresh mind. He had school, but he couldn't give two fucks about that, he had to make this work, so he went with the usual clone-substitute. He just simply wasn't able to wait anymore.
The next morning he woke up with high spirits and after a brief breakfast and sending his clone to school he rushed to a blacksmith. He knew he will need to make his own kunais that he can put his formula on. This was also the practice of Minato who enchanted his kunais so he can teleport to them too. This way in a battlefield he can throw his kunais around, simultaneously attacking and creating more and more exit points for his jutsu. Dix intended to do the same, it was a great way to fight.
He gave the order to the blacksmith, who had a hard time understanding why would someone need kunais like what he was told to make. Dix had a specific design in his head. He remembered the kunais that were in the game he played a lot when he was young, its called 'Warframe', in which you control space-ninjas and go on missions with them. He remembered quite well how those kunais looked. They had no actual handles, but only the blade part and a ring at the end. It was mostly used for throwing, because the lack of handle made it impossible to use for close quarters combat slashing or stabbing. This is exactly what Dix needed the kunais for. To throw them around, this design was the best, while also small and easy to handle.
He was told a dozen will be done in a week, and if he is satisfied with the outcome, then he will be able to order more later. That was good enough.
With that done he had to go back to his apartment to start working on his formula. He would've gone out to his camp in the woods, but it was school time, and the guards would've asked why is he trying to exit the village while he was supposed to be elsewhere. But not a problem, creating the formula itself wasn't dangerous or required much space. He had a limit of how many clones he could summon though. He didn't need many of them though, he just had to create a formula that would emit a signal, not practice stuff just yet.
Dix was hyped as heck, so he dove head-first into the first step of the jutsu.