This shinobi world was fascinating just like the world that he came from and there were many things that existed in these worlds that the humans were not aware of or could not explain.
There were many who tried to study, research and explore these unknown marvels, and Rei was one of them, an Archmage who had explored the marvels of his world and reached the pinnacle, or at least that's what he thought when he had died.
But after reincarnating he realised the world was much bigger and more mysterious than he had imagined, but this did not discourage him instead it woke up the sleeping thirst he once had, to study and explore the unknown.
He simply wanted to know more.
..
If one wanted to tread on an unknown path they had to be ready to dirty their hands, especially in a world filled with wars and death, afterall the path of a pioneer was not a walk among the flowers contrary to what some ordinary people may believe.
Rei had killed a lot and studied enough bodies in his previous world to remember every part of the human body thoroughly.
Although some of his memories seemed blurry most of his knowledge was still intact.
Although chakra was an energy that followed different principles compared to mana they still held some similarities, they both flowed through the human body in a somewhat similar fashion so Rei believed that the idea that he had for a new jutsu could come to reality, although this jutsu might already exist somewhere in this world, it was faster and better if he created the jutsu on his own.
He had been working on the jutsu for a while now but the progress was too slow since he had to be very careful when he experimented with the jutsu on himself, but now that he had a subject to work on he didn't have to be so careful.
Rei meditated as he brought his concentration to the peak after he finished his preparations, a habit from his old days.
His hands moved swiftly as he started to form hand signs while he weaved his chakra between them.
As he kept his fingers on the head of Iwa shinobi black markings appeared and started to spread.
When they had almost covered his whole face the markings stopped spreading.
"It stopped."
Rei who was observing this phenomenon keenly stopped for a while as he analysed what had happened and adjusted the formula for the markings and continued what he was doing.
..
"Stopped again."
Hmm!
"This seal is hindering the flow."
He was stopped again so he removed the faulty seals and added something that would work.
..
"Stopped again, hmm."
He realised that the base formula was working but it was lacking some seals so he adjusted the formula and added some more seals.
..
Mistake after mistake.
He continued to make mistakes.
From 10 to 20 seals from 20 to 40.
But each time he resolved his mistakes inspiration also flowed in.
His hands moved like an experienced artist who was not satisfied with his work of art.
As he continued to add more and more seals the formula started to get much more complex and the seals covering the shinobi's body continued to spread.
He also had to remove seals time and time again or adjust their positions.
A few hours passed in the blink of an eye as Rei was immersed in his work.
But he continued to get excited with each success, although his face was as calm as ever the glint in his red eyes continued to deepen.
His face was covered with sweat and his chakra levels continued to drop.
While he was busy yhe shinobi had also woken up and he looked completely terrified.
But he could neither move nor speak, Rei had made sure of that.
Rei used a simple genjutsu and put the shinobi who could not resist to sleep again and continued his work.
The number of pitch black seals covering the shinobi's body had already crossed 50.
50 to 60 and from there to 80.
At this point even Rei thought he was overdoing it, but he knew something was still missing from the formula.
It is said that humans learn from mistakes, and Rei was learning with each mistake he made.
"Huff, lets stop and think for a while."
He stopped and let out a big breath as he closed his eyes and thought about the formula again from the scratch.
'The chakra gathering seals have no problem the storage should work fine as well but the flow is still not working properly, specifically around these eight tenketsu points, the eight gates.'
'I think I can solve it if I avoid using these pathways but I don't want to since that would increase the number of seals to almost a hundred and would be very inefficient.'
'What if I unblock these points? No although it seems like this would give a huge chakra boost in the short term, it would just lead to death later since the chakra flow would become unrestrained and the body would suffer huge damages.'
Although he had a few solutions in his mind they were not to his liking.
Although it was interesting, Rei could not guess how big of a chakra boost he would get if he released the eight gates nor did he want to try and find out since his body was too weak and he would just die a meaningless death, although it would seemingly solve this issue it was not like he could always have these tenketsu points open and it didn't seem it would be easy to open these points either.
'It would probably take years to open them.'
If he avoided these specific pathways he could solve the issue by increasing the number of seals but that seemed like a desperate measure to him.
These points were like a valley blocking the flow of a big river.
'Wait what if I transport the chakra from one end of the tenketsu point to the other directly.'
"Hmm that should be plausible."
'I need some seals act as links that would overlay the eight gates, if the eight gates are like valleys these seals would act as a bridge.'
Rei could not help but smile at the sudden inspiration.