"I studied [Heavenly Restriction], the kind that sacrifices Cursed Energy in exchange for physical strength, for quite a while. Although Toji Fushiguro refused to let me study him, I still managed to learn a lot about it...
Based on the information Akira Zenin gave me, Maki Zenin's 'exchange' was not extreme. She still retained some Cursed Energy.
Historically, the other people with [Heavenly Restriction] were not like Toji Fushiguro either. None of them completely gave up their Cursed Energy the way he did.
But because Maki Zenin is a twin, her [Heavenly Restriction] is actually incomplete. There may still be room to keep 'refining' it further and turn her into a 'superhuman.'
Twins are treated as a single person within the system of Jujutsu. That leaves both of their individual 'systems' incomplete, which creates a situation where they end up holding each other back.
The so called Twin Complementation is to make Maki Zenin and Mai Zenin, the two halves that were split apart in Jujutsu terms, become two separate and complete individuals again."
"Hm, so why exactly did you call me here?"
Naoya Zenin casually straightened his collar and leaned against the railing to the side.
Yuki Tsukumo had called him over using the excuse that "Akira Zenin wants to see you," but after arriving, not only did he fail to see Akira Zenin anywhere, he was instead left standing there listening to Yuki Tsukumo explain Maki and Mai's situation.
If his temperament had not grown steadier lately, and if these two were not people Akira Zenin had once gone out of his way to protect, he would have stopped listening long ago...
"Yuki-senpai has not finished yet. Just listen."
Noritoshi Kamo, who had also been called over, looked straight at Naoya Zenin and cut him off before he could interrupt Yuki Tsukumo again.
"Heh..."
Naoya Zenin glanced at the future head of the Kamo clan. He knew the man was strong now, but without Akira Zenin's guidance, reaching Grade 1 would probably have been difficult for him. In Naoya Zenin's eyes, Blood Manipulation was only so so...
"There is obviously a reason I called you here."
Yuki Tsukumo was always unusually patient with anyone involved in her experiments. She was not the type to put on airs just because she was a Special Grade Sorcerer.
"Before we can understand the true nature of the Jujutsu system, completing the two of them will require a fairly crude kind of reverse deduction.
Whether it is Cursed Techniques or Cursed Energy, both are imprinted onto the human body at the moment of birth. The ages of six to eight are simply when they begin to manifest.
And if we want to change [Heavenly Restriction], then we have to go back to before [Heavenly Restriction].
In other words, the problem starts before birth, so we just have to let them be born again... and that will require some help from the two of you."
"Go back to before birth? What, are you asking me to beat them back into the womb so they can reincarnate??"
That was what Naoya Zenin said, but he leaned forward slightly, clearly interested.
Noritoshi Kamo, standing beside him, continued listening quietly.
Yuki Tsukumo took out two small notebooks and tossed one to each of them.
"Here. Akira gave these to you. He said that, as genius Jujutsu Sorcerers who have studied barrier techniques since childhood, you should have no trouble understanding them."
Naoya Zenin and Noritoshi Kamo each caught a notebook, and for once, even their movements and expressions were strangely in sync.
Compared to ordinary Jujutsu Sorcerers, they were indeed strong, but hearing the word "genius" from Akira Zenin carried a different weight...
Akira Zenin was the kind of person who was actually stricter with those close to him. Praise that simple and direct was something they had almost never heard from him.
Just as Noritoshi Kamo started flipping through the notebook, Naoya Zenin suddenly looked up at Yuki Tsukumo.
"Um... can you say that again?"
Yuki Tsukumo folded her arms and rolled her eyes.
"These are from Akira. He said that, as geniuses who have studied barrier techniques since childhood, you should be able to understand them easily.
Oh, and he also said you should be able to figure all this out within two hours."
The moment Yuki Tsukumo finished speaking, Naoya Zenin started flipping through the notebook at astonishing speed.
She shook her head helplessly. If he could really understand something like this at that speed, then he really was a genius... Oh? He is even using his technique already...
...
After some time, Yuki Tsukumo brought the two test subjects to the back courtyard of Tokyo Jujutsu High, and Naoya Zenin and Noritoshi Kamo were both ready.
Unlike before, both of them were now visibly excited, because what they were about to attempt was something never recorded in the known history of the Jujutsu world. [Double Domain]
"To return to the state before birth, the first step is to isolate them from the world, and the clearest form of that isolation is a Domain."
Yuki Tsukumo nodded as she looked over the two of them. The test subjects were in good condition, and so were the experimental tools. That Akira brat really did know what he was doing. Everything was going according to plan...
"After that, all we have to do is synchronize every piece of information their bodies need to share, their heartbeats, their cellular states, everything, and then separate them... Akira Zenin should have mentioned it in those notebooks. Your Domains have a high degree of compatibility, and they just happen to meet all the necessary conditions.
It may even be that Naoya Zenin's Domain exists for the sake of separating the Maki and Mai sisters..."
"Hah? What kind of nonsense are you talking about??"
Yuki Tsukumo shook her head.
"Nothing. Just thinking about fate..."
She then turned to the test subjects, who had remained silent the whole time.
"What is it? You are about to become 'complete,' so cheer up a little."
Maki nodded, then glanced at Mai, who stood beside her with both hands clenched into fists in nervousness.
"It is just that... the way you said 'letting your sister leave your body' does not sound very good."
"Hah~ Relax, relax. You will still be sisters. We are only cutting the connection created by Cursed Energy~"
"Mm..."
"Ready?"
All four people present nodded. Maki and Mai walked to the middle of the courtyard, while Naoya Zenin and Noritoshi Kamo stood on either side of them and began constructing the "double barrier" described in the notebook.
"Domain Expansion. [Time Cell Moon Palace]"
"Domain Expansion. [Funeral Chamber of the Heart]"
A double barrier was not a simple inversion of inner and outer layers. It was something woven together within the original Domain barrier itself. And on their very first attempt, the double barrier they created was astonishingly complete. If the long armed demonic virtual Mahoraga who developed this thing were here, he would probably be nodding in satisfaction from the sidelines...
If, on top of the double barrier, the two people's innate Domains were projected at the same time, and if those innate Domains were sufficiently compatible, then what would form was [Double Domain].
And this, right here, was the double Domain designed by Akira Zenin, with Naoya Zenin as the core and Noritoshi Kamo as support.
"[Fusion Cell Primordial Womb]!"