Correcting one's faults

Last month was Tetsuo Katsuo's birthday, he is fourteen years old now.

The last few years passed very quickly to Katsuo, and even though he made progress in everything, especially in his physical body, which was as powerful as Itadori after eating two of Sukuna's Fingers, and cursed energy capacity, that was as much as around 85% of Gojo's.

He also learned how to do the barrier technique [Curtain] and how to draw some talismans, it took reading a ton of books but now he could summon shikigamis and make seals. The shikigamis he could summon were pretty weak so they were pretty useless, but their vibes were familiar to Katsuo. He tried to trace that feeling and, in a second, he remembered that he once hunted things with those vibes and was a little embarrassed. One book that Gojo gave him said that shikigamis are used as reconnaissance. It seemed that he killed those shikigamis on his hunts.

(AN: Do you remember for what reason Gojo was dispatched to kill the only special grade curse that Katsuo fought?)

He also managed to learn the [Simple Domain] or "domain of the weak". Gojo said that as he still wasn't ready for using [Domain Expansion], it would protect him against his enemy ones, so he should learn it. Katsuo, who saw the anime and experienced a [Domain Expansion] himself, of course agreed and learned it quickly, so that he at least had a defensive means against special grade curses and sorcerers, even though he couldn't move when he used it.

He accomplished a lot in these years but even then Katsuo was not satisfied.

His [Reverse Curse Technique], as a result of devoting a lot of time to it, could be used to heal himself of minor non-fatal injuries but was nowhere near to heal fatal ones like Gojo, he thought that Gojo was really lucky to have [Six Eyes], that kind of cheating engine. Of course, Katsuo didn't know that it wasn't easy for Gojo to figure out how to perform it and only did on the verge of death. Gojo was also quite impressed that Katsuo managed to perform it after only listening to the theory and training for a few months.

Eventually, Katsuo, seeing that he was not progressing much in it, put it aside and focused on developing his innate techniques and in there he found difficulties too.

Katsuo managed to amplify his [Inventory Stomach] and its effect was that he could stretch his mouth to bigger proportions, meaning that he could put bigger stuff in it. It was gross before and now it was even grosser. Katsuo named it [Inventory Entrance Expansion], a rather "cute" name that didn't fit how gross the technique was in his opinion.

Until then everything was going well but then, on one of his lessons with Gojo, he asked.

"Gojo-sensei, does your [Limitless] have other derivative techniques that you didn't showcase me yet?"

Gojo made a thinking pose and said.

"Hmm~, I do but why are you asking?"

Of course, Katsuo knew that but that question was the preparation for a request he had.

"I want to know the principle behind them and see if I can apply it to my innate technique!"

Gojo thought for a moment with his hand beneath his chin.

"I can teach you the principle behind them but don't get your hopes high, I can do it because I have my [Six Eyes] so I don't know if you can do it."

Katsuo became a little upset after he heard that but the confidence or maybe even arrogance he gained and developed since his birth until that moment wasn't that easily beat down, so he looked at Gojo determinedly.

"I would still like to try!"

Gojo looked at his confident student and grinned.

'This will be a good lesson to him.'

"Well, why not, I have these derivative techniques... and this is how they work ..."

(AN: Go see the fandom)

After his lesson with Gojo, Katsuo was amazed. He understood in the anime that what Gojo did was miles ahead of any other sorcerer but it was only now, after being in contact with CE himself, that he understood how amazing he was, and Katsuo also understood why Gojo thought he couldn't do it.

The precision of CE control needed to execute them was so high that an impossible fluke was needed for him to be able to execute them. He basically needed to run the innate technique without wasting or using more than the minimal CE amount needed. That action brought the consumption of the technique to basically nothing and made it possible to completely maximize the technique's power and effects, and that kind of control also made it possible to perform the innate cursed technique with positive energy instead of CE and use [Cursed Technique Reversal].

Katsuo understood all that but he still tried, and tried and tried, all without success.

Katsuo was becoming increasingly angry, causing him to frequently lose control of the CE.

Suddenly, Katsuo stopped.

'Something is wrong with me.'

He realized that lately, his emotions have begun to affect him a lot and he was becoming less and less reasonable. After thinking for a while he reached a conclusion.

'Puberty.'

Puberty has made his emotions unstable, causing his temper to become increasingly worse and his mind more narrow-minded.

He thought long and hard about that problem and tried to come up with solutions by cross-referring his problems with the knowledge he gained from Gojo's books and eventually reached a solution that he thought was the best because it gave the most results.

'From now on until one year later, I won't use CE any longer except for CE manipulation training, I will use this year to temper my will, train my emotional control and my CE manipulation, I will start again from the basics.'

As he made that promise to himself, Katsuo felt his CE becoming restrained and instantly realized he just made a Binding Vow, and with rapid thinking, before his CE become completely restrained, Katsuo, using [Inventory Stomach: Inventory Entrance Expansion], expanded his mouth to ridiculous proportions, ruining his handsome face, and "vomited" out all its contents, which included his smartphone, which he needed daily, pills that could sometimes be essential and more importantly, a cursed knife, a birthday present given by Gojo, to hunt curses with.

'Thank god no one saw!'

Thought Katsuo as his face returned to normal.

On the next lesson with Gojo, Gojo realized that something was wrong with Katsuo's CE, like it was being restricted by a Binding Vow, so he asked what he did and Katsuo explained the conditions of his vow.

After hearing the explanation, Gojo put his hand to his forehead while bending his neck backward and grinning as if thinking something was funny.

"That's super hilarious, Katsu-chan, but that's the way, if you want to reach my level, you need to take those kind risks and decisions."

Gojo actually felt that this kind of restriction could have really good results on someone as talented as Katsuo, and he was looking forward to how much improvement Katsuo could show him one year later.

From then on, Katsuo trained himself in the basics from scratch while also training his sister that made some good progress these last years. Her CE manipulation and capacity reached a good standard, and she could make an aesthetically pleasing biological-like armor with an exterior layer of black bone plate protecting the vulnerable parts and an interior layer of purple muscle fiber spread all over her body color that could enhance the power of her blows and movement speed.

(AN: His sister is 8 now. Drop here the appearance of the power armor, normal people can't see the armor because it's basically CE turned into curses' flesh and bone, which normal people can't see)

Even though she was not nearly as good as he was in her age, he was proud of her progress.

He also showed some curses he caught to get her used to them, after all, she could always see curses but because he exorcised all the ones surrounding his neighborhood, she had never seen one before, so by getting her used to it, she wouldn't be scared when she encountered one later.

Of course, he didn't forget to tell her how powerful curses could be and she should never willingly involve herself with one, instead, if she saw one she should call him and he will deal with it.

He also focused Yua's education on morals and the difference between normal people and sorcerers, so that she could still function as a normal person and if for some reason she used her powers, it will be for good.

He also thought about Tokyo Jujutsu High, the school Gojo said he would take him to when he entered high school, and as he thought about it, he realized he should have a talk with his parents about it.

'I will talk to them tonight.'