Time flies by, the fruits of hard work
Dix finished most of his major businesses, and now he just needed time to progress his ongoing projects. Something which he had a lot of. Considering his amazing speed of growth, 4 years are more than enough for anything. He had to press hard on studying seals, also with his now pristine physique he could start opening the Eight Gates in his body.
Seemingly the first few gates are incredibly easy to open, even for someone who doesn't use shadow clones. So Dix had a really easy time. The Eight Gates are major chakra nodes in the network, which are primarily there to restrict the flow of chakra. All he had to do was forcibly open the restrictions by pushing enough chakra trough the limiter. When the gate bursts open it will stay that way until the user consciously uses inner chakra control to close the gate back. As long as its open chakra can flow unrestricted, meaning the user gets access to incredible amounts of chakra that are usually locked by their own body.
As the gate opens the chakra will start flowing both inside the body, and would start heavily leaking outside too, as the gates are unable to stop it from escaping. This is one of the reasons why the technique itself is considered forbidden, as even the activation of the first gates will leave the user heavily exhausted.
Dix wanted to overcome this huge problem with seals. He planned on using his clones to perfectly seal up every single one of his tenketsu points, the nodes of his chakra network, from the outside, meaning the flow inside the body would continue undisturbed, while there would be no possibility of leakage and the escaping chakra gets forced back into the body. This was his number one priority.
Thus, after around 7 months of hardcore training and studying with approx 150 clones he felt like he was ready to begin the procedure. He considered the problem from every angle, he consulted with every book he found on the matter, and he felt quite prepared. He already mastered the first four of the Eight Gates. One day, after his 5th birthday he lied down on his back in the woods on a wooden table he crafted, as he had many clones summoned to handle the procedure.
All he had to do was keep himself steady as the clones drew on his body extremely carefully and in as small characters as possible. There wasn't much space, so they had to make absolutely sure they are drawing the right thing at the right location. They had to draw endless cyclic and intertwining lines on almost all available surface on Dix's body. There are 361 tenketsu points which were extremely tightly packed on his body, and among them the Eight Gates needed special formulas to handle the extreme load. There the seals worked like if the seal was about to lose its power due to the huge amount of chakra trying to escape, it would absorb some of if to repair its integrity. This would mean as long as he has chakra, the chakra itself wouldn't be able to leave.
This poses a huge problem though. If he was to permanently seal his body, then how would he be able to use jutsus that require outside chakra control? Well, obviously, he couldn't. That's why he had to research a lot, and even innovate some on his own. He managed to figure out a way to 'lock' and 'release' the entirety of the seal array on his body with a specific chakra group that had special intent in it, which he was able to make himself. This would have to be inserted into a specific part of the array to basically turn on and off the whole system, like a key. With this he had to engage the seal right before he starts using the Eight Gates technique, and release it when he was done, or needed something else. He could even turn it on and off while the technique is going, to use outer chakra jutsus at the cost of losing huge chunks of chakra.
After all that considered, he put together a great seal to overcome the weakness of opening the Eight Gates. It was obviously not perfect, there were various ways to improve. But he had no access to better technology and didn't have enough time to perfect it himself. He just wanted it to work.
When the clones finished writing up every single rune and sigil on the entirety of Dix's body that was supposed to be present they all started injecting huge amounts of chakra into it. It was able to keep itself powered as long as chakra was provided to it, but at the setup it had to be heavily infused with a chakra on specific locations to kickstart the process. When the chakra was about to reach its peak and the seal was supposed to start, every part of the seal started glowing blue, then it... vanished. The clones started worrying and every active dispersed immediately except two which stayed to be able to provide outside help for emergencies.
Dix got scared for a second too, but when he scanned his body he noticed the whole array was there where it should be, but it seemed like the 'default' state for the seal was 'off', which made it invisible for the naked eye. Dix stood up and started circulating chakra throughout his whole body. He checked every single cell for chakra connectivity, and it seems the seal didn't affect the inner network at all, just as planned.
Now he wanted to try and turn on the seal to see if that function works properly. He followed his own instructions engraved into his head to the letter. When he got it done the seal suddenly appeared, but he didn't notice any change. He scanned trough his whole body one again, and it was still operating as expected. With that done he wanted to see the actual main function in action.
He opened the first gate, the Gate of Opening. He tried to check the gate itself trough his inner vision, and he was satisfied to see there was no leakage visible. He started opening the gates one by one up to number four, the Gate of Pain. Between each gates he waited to see if the seal was working properly and if there are any problems with it. He found no bugs, but at the fourth gate he could feel that the whole array was trembling slightly, almost imperceptibly. He understood, that later stages of the gate might put too much strain on the seal and he would have to upgrade both the technology and the quality to progress after probably the 6th or 7th gate.
He wanted to see the performance of both the fourth gate and the seal in action. Thus he started rushing trough the forest at maximum speed. He was having fun, but he couldn't lose focus whatsoever, as even a slight mistake would make him fly trough many trees at once. He was running so fast he was almost invisible. He only left behind afterimages, and even a jonin's eyes would probably have a hard time following him. Only special eye-techniques would be able to keep up, for example the Uchiha's Sharingan or the Hyuga's Byakugan.
After some running he started punching stuff. First trees, but those were quite weak and broke in two by a slight tap, so he had to try rocks and boulders, but even those couldn't resist. He didn't actually have any way to confirm his limits anymore, as he outgrew the forest way too much. During the test he had many clones to watch his performance and scan for leakage or problems.
When he ended the technique he was still able to feel the aftereffects. His chakra reserves barely dwindled, but his muscles were strained the same way as before. This was also a problem of the technique, but his body being infused with chakra 0-24 and being acclimated to the these strains since birth, his muscles had way better endurance and could regenerate way faster than any taijutsu genius' that ever tried this technique. He decided he would have to extensively train his physique whenever he manages to unlock a new gate to get his body used to the strain.
Soon he was doing all of his physical exercises using the fourth gate and his body was rapidly changing to accept the new challenges. Once again, his body is of a 5 years old and was still in a growth spurt. His body would've kept changing and growing either way, its just this time he was able to lead the direction of the changes.
Chakra itself is so marvelous it is hard to describe. It kept reconstructing every single part of his body to better their chakra connectivity and capacity. It even strengthened the muscles and heightened their density by a lot. Chakra was the fiery crucible that was about to melt Dix's humanity and reshape it into something way better. This came with a lot of pain though. But he held out and was getting stronger and stronger with each session. Even he himself began to think its a bit too fast, but there are no brakes on the train train. He had to keep doing his best, keep pushing trough his boundaries. The sky was the limit, and he intended to grab all of it.