Since both Yomi and Karin would need over one more month to be at Kaida's level, Kaida was free from learning fuinjutsu for 1 month at least.
So deciding to put his focus on other things and get to work into mastering his already learned jutsu with the help of shadow clones, while he himself decided to completely focus on Mitotic Regeneration Seal. It was supposed to be his trump card, an almost limitless reserve of chakra, but what he got for now was a reserve not even similar to his own chakra capacity.
So while his clones were focusing on mastering various jutsu including Kenjutsu, he was renting the best meditation room in the Uchiha clan to focus on Mitotic Regeneration Seal.
...
Kaida was sitting in the completely closed room where even the door blended with the wall, giving a feeling of being completely cut off from the outside world.
On his forehead, a black rhombus was glowing with a slightly red glow, and even with his eyes closed, the subtle glow of Sharingan was visible.
He had already seen how Sharingan helped in pushing chakra in the seal, and since now he had a version of Sharingan which was obviously superior to the three tomoe Sharingan, it would be blasphemy to not check the new potential for increasing his backup chakra reserve.
So, he was using the Mangekyō Sharingan solely to control the chakra within his body and push it into the seal. It was like trying to fill a pot with water while a porous rock sat on top of it. If you poured too quickly, the water would spill off; too slowly, and the rock would absorb it. You had to maintain a perfectly consistent flow—one that matched the rock's absorption rate.
But the Mangekyō Sharingan bypassed that obstacle entirely. It was like increasing the water pressure to such an extent that it forced a hole through the rock, making it much easier to fill the pot. However, this method was incredibly taxing. If any other Uchiha—especially Fugaku or Shisui, who understood the cost of using the Mangekyō Sharingan—ever found out, they'd lose their minds over Kaida's recklessness.
But Kaida had another reason for doing this. A shadow clone stood beside him, constantly monitoring his condition while the Mangekyō was active. Kaida was using this opportunity to study how the Mangekyō Sharingan would affect him over time. Could he use it ten times before his eyesight deteriorated? A hundred? He needed to understand the price of using it in battle—before anything major happened.
While Kaida had kept MS active for almost 20 minutes, his clone was constantly monitoring the condition of his eyes. After 20 minutes, he had pushed almost half of his chakra reserve into the seal, while 30 percent was used by MS itself, leaving him with only 20 percent of his chakra reserve. Since the chakra represented the physical and spiritual energy of the user, having only 20 percent of it felt like he had just run a marathon in the summer afternoon.
But his focus was not on that. As soon as he stopped pushing chakra into his seal, Kaida deactivated his MS, and the clone did a last scan before dispersing itself, leaving behind notes of the observation of 20 minutes and memories.
'So my eyes did get damaged, even though I didn't even use any major ability of MS, but the damage was minimal, like watching the sun for 20 minutes. Now let's see whether it is reversible or not,' Kaida thought and created a shadow clone which went directly to work. Slowly but surely, all of the damage from using MS was reversed, almost to a perfect condition... almost.
'99.5 percent damage healed, but some is still left. That means even though it is reversible, it is still not completely curable. That means if I use this excessively even without using MS abilities, I will go blind, but at this rate, even with daily use, it will take a decade for that to happen.'
"We still need to check for the abilities, especially our Susanoo. It will be a crime if we can't try that," Kaida's shadow clone said.
"But if even simple use like this is damaging the eyes this much, I don't want to use Susanoo and other abilities without any reason," Kaida said, thinking.
"But we can't just wait around to test them out—we need to know the actual damage they can cause, so we'll know how much to use them in battle, right?"
"Yeah, but still, now's not the right time. I'm not even planning on taking any big missions for the next six months," Kaida replied with a smirk—one that mirrored perfectly on the face of his shadow clone as it caught on to what Kaida meant.
It was like talking to oneself, but with a voice and real interaction. Probably one of the best uses of the Shadow Clone Jutsu.
While Kaida was finalizing his experiment, his clones had been busy with two things. First, around thirty clones were busy practicing various jutsus including Kenjutsu, ninjutsu, as well as genjutsu. Then, other thirty were working on the stadium or 'Colosseum' construction project which Shinji Nara had specifically asked to name it as.
With thirty ninja of Kaida's caliber working on the construction of the colosseum, the process was moving forward at full speed.
Impressed by the efficiency of the training, Kaida decided to stick with this schedule for the rest of the month. He continued using his three-tomoe Sharingan, which had become significantly easier to manage after awakening the Mangekyō Sharingan.
Thanks to which, the process of filling the seal with backup chakra was going very smoothly, and due to his efficient training while working on the construction of the colosseum, that was also coming along nicely.
For a whole month, Kaida stuck with the same routine, only going back to his house in the evening. Due to Hiruzen's order, Kimimaro had to stay at home all of the time, and the number of ANBU ninja who were stationed around their house for the security of Naruto had also increased in number.
Kaida noticed them the first time they appeared. The thing that would freak other people out a little, as being watched by someone 24/7 was a little unsettling, for Kaida it was somehow very comforting.
Even though his house was covered with seals made by both fuinjutsu sealmasters of Konoha, as well as an Uzumaki herself, which made it one the safest houses in whole Konoha, there was no amount of security enough in this world. So having a few ANBU ninja watching your family while you were busy with other things is not a bad deal at all, especially since they don't even know about them. Kaida was pretty sure Shisui would notice them as soon as he came back, but since he was also on the same boat as Kaida, he would also most likely be happy about this.
So with extra security at his house, Kaida kept his training going, while Yomi and Karin were grilled by Reina for their fuinjutsu practice. With Yomi at Reina's and Karin's house, Hae at the bathhouse, Naruto at the academy, and Kaida training, only Kimimaro was the one who had to stay at the house.
But he never said or showed any problem towards that, or one can say he didn't even notice that. When Naruto told him that he had already learned so much and someone at Kimimaro's age should know much more, he somehow became motivated to crack the entrance exam of a top university or something, going through books like they were children's stories.
For some reason, seeing someone like Kimimaro, the young deadly genius immersed in books, was both awkward and heartwarming.
Like this, a whole month passed and the ninja who went with the daimyo were now back in the village, though surprisingly the first person to come and meet Kaida was not Shisui but... Jiraiya.