The moment Gojo entered with Nemu and Soi Fon behind him, he couldn’t help but shiver a little at the sight that greeted him.
From a normal perspective, If Garganta was a vast empty field, then Dangai could be likened to a long endless tunnel. The ‘walls’ of the tunnel were a row of dark clouds. Clearly, this place was rather normal-looking.
But for Gojo, this place looked more like a giant death trap.
The cloud walls weren’t harmless. They were called Koryu and were deadly traps for all spiritual life forms. Should anyone enter in contact with it without proper preparations, one would be rendered completely immobile immediately.
Of course, Gojo was no exception. If any part of his body got trapped, he would have to immediately cut that part. Otherwise, it would be game over for him, as he would be trapped until the Kototsu came and sent him back to the past, but because of the high distortion, his body would be completely torn and reduced to nothing. 
“So, Dangai was your goal all along.”
Soi Fon, who had until then stayed silent finally spoke. Her power of observation was rather high. Otherwise, she wouldn’t work as an assassin and spy. This was why she was able to see that Gojo didn’t enter Dangai to complete the mission, but because Dangai itself was his goal.
She could also understand why he had needed her to follow him,
“You need a captain level to stop the current.”
“Bingo! No prize though.”
Gojo shrugged and did not try to deny Soi Fon’s deduction. He wasn’t surprised that she got it right. After all, at this point, it was pretty obvious.
“Gojo….Do you know why no Shinigami tried to use the Dangai for such a purpose?”
“Because of the Kototsu?”
“It’s one of the reasons.”
Soi Fon, showing a bemused expression, tried to explain the situation.
In the first place, the only way to stop the Koryu was to either channel the Reiatsu of a captain, or to use some special instrument. By doing so, one would be able to obtain a great amount of time. But here lied the problem.
How long could the torrent be stopped?
“Some captains in the past tried, and the best they could do was to stop the flow for about 1000 hours in Dangai time, or 30 minutes in the normal world. For the instruments, it was even worse, and stopping the flow for even 10 minutes in the normal world would be difficult.”
The price was that the captain would lose all combat capacity for about six days. Meanwhile, the Kototsu shows up every seven days. It means that one could only use it once every week. Just to get about one month and a half.
“Now let’s say that it would be possible to increase the number of captains. How many of them would be willing to tire themselves out and be put in a situation of danger for nothing? Even if all the captains were willing to work for you, in the end, after one year in the real world, you would have only trained for about forty-four years.”
Nemu listened without interrupting. As the vice-captain of the 12th division and the direct assistant of Mayuri, she had a deep understanding of this problem.
It wasn’t just about fighting. Some scientists wished to use the flow to their advantage to increase the amount of time they had at their disposal. In the end, the project was scrapped as the cost to maintain it was too high and the slightest mistake could mean death.
Soi Fon, meanwhile, didn’t stop.
“But all this is just a question of dedication. There’s another more fundamental problem. Even though Shinigami need time to master and adjust to some skills, time itself is not a factor of strength for us. Once we reach a certain level, time itself is meaningless. Shinigami cannot grow indefinitely after all.”
Gojo nodded, if the growth of a Shinigami could be traced in a curve, one would see that the growth was in no way stable through time but rather needed a special trigger, then was followed by a sudden peak increase in strength.
An average shinigami could suddenly become a master if he awakened a powerful Zanpakuto. The same went for Bankai.
If a shinigami had no talents, even if you gave him hundreds or thousands of years, the result would be the same.
At most one could argue that it helped greatly reduce the time needed to master some skills.
Time was indeed meaningless for Shinigami. For example, Unohana was not much stronger than her past self during the creation of the Soul Society. In fact, from her words, it seems like she had weakened instead.
This was the innate limit. Something that could never be surpassed and that limit determined how far you could go, not the time you invested.
This was the kind of world this was.
Soi Fon finished her explanations and looked attentively at Gojo’s face. The reason she explained all this was because she wished to see the expression of disappointment as he realized that his master plan was in fact a failure.
She was sure that since Gojo was a young Shinigami, he had been dazzled by the notion of Dangai and thought the only reason it wasn’t used was that it was forbidden by the law.
All this while, seeing his assured and arrogant face had ticked her off greatly. This feeling was increased by the current situation she found herself in. After all, even if she wasn’t flustered by having a bomb inside her body, knowing that her life wasn’t her own gave a pretty shitty feeling.
Unfortunately, she was bound to be disappointed. After all,
“I already know all that.”
“Heh. Did you really think I would rush headfirst without a thorough plan? I may be prideful, but I am not stupid.”
Of course, he knew. How could he enter this place without wondering why no one ever made full use out of it? In the end, the risk and cost of using Dangai far outweighed the possible gains. 
But Gojo didn’t care. He didn’t wish to use Dangai as some sort of time chamber to accelerate his training. He needed to go to Dangai in order to feel the distorted flow of time and see what he could glean from it.
He hoped that he would not be disappointed.
Turning towards Soi Fon, he asked,
“Will you help me?”
Soi Fon, who was disappointed by the fact that she wouldn’t see a downcast Gojo tilted her head at his question,
“Why don’t you threaten me?”
“I already told you that I have no wish to threaten you. Aside from asking you to keep my secrets, I will not leverage the bomb whenever I need to ask you something. You are free to refuse any request coming from me.”
Gojo knew more than anyone that blackmail and threat were a form of art. He wasn’t above using any of them, but they had to be used in the right way on the right person. The most important was to never break the bottom line of the one you were threatening.
For example, even though he forced her to not reveal his secret, since she did not think that he had nefarious intentions toward Soul Society she did not try to fight back, as she judged that sacrificing her life for this was not worthwhile.
But what if he asked her to betray Soul Society? He was pretty sure that she would kill herself immediately.
At the same people, companions that had been obtained through unorthodox means were not trustworthy.
“Then, let’s make a deal. I will help you, but in exchange, you have to take away that bomb.”
“Give me forty years. I will erase my Reishi in you by then.”
Soi Fon did not miss the implication in his words. Gojo did not want to show his Bankai because he would most likely get sent to the Maggo Nest.
“You believe that after forty years, no one will be able to threaten you.”
Gojo smiled confidently, “That, I do not know. But I am sure that after 40 years I will have reached a level where few people would even be able to touch me.”
Soi Fon thought he was speaking figuratively. She did not understand what kind of Gojo was reaching for.
Gojo knew that Limitless itself was not that incredible in this world. But it was mainly because Limitless was hindered by his frail human body. Right now though, be it his physical abilities or calculation speed, he was incomparable to his past living self.
“Are you not worried about me suddenly pulling out my energy and letting you trapped in the flow?”
“Trust is something that goes both ways. I trust that you are not the kind of person to do such things. But more than anything—I trust myself.”
The meaning was clear. Even if he focused entirely in training, he still believed he could deal with anything she might throw at him.
“…Very well. What should I do?”
After a tense silence, Soi Fon finally relented. She did not know if what she was about to do was the right choice or a mistake. But she would take one step at a time.
Smiling, Gojo’s expression barely flickered as he felt someone pass through the gate he had intentionally let open.
How could he let another captain level escape his grasp when he needed so much currently?
: Wrestling flow
: Wrestling surge
Pretty easy to understand, but if I had to give an example, those who watched or played Stein gate should understand what happens if you time travel in the wrong way. Imagine that, but rather than some green goo, there is nothing left.
 Isshin could stop the flow for 2000 hours or nearly 3 months which was one hour in the real world.
 This explanation wasn’t given in Canon but is born from my own understanding of Bleach. In Canon, the only reason they gave was Kototsu and Central 46 forbidding it. But I think it’s mainly because Shinigami don’t need time for power-up. Though they need time to master skills. One example is Toshiro/Rukia/Renji. Toshiro entered the academy five years after Momo and Renji etc did. But they graduated at the same time and when they were still vice-captain, Toshiro was already Captain and had Bankai. Another example is Child Zaraki vs Unohana. As a child, Zaraki fought on par with Unohana when she was still a Kenpachi without even using Shikai and only lost because he subconsciously made himself weaker. Finally, the best example is Ichigo. XD in two years the guy reached the level others took hundreds or thousands of years to reach. The worst is, it isn’t even two years, since he stayed 17 months without power. So in just one year, Ichigo went from human level to galaxy destruction and possibly universal level. XD
(AN: Man, setting up a power-up isn’t easy. You wouldn’t believe the amount of research I had to do in order to create something logical and badass. Making the relationship grow is even harder. Yoruichi will act as a lubricant. Later)