The 4 fundamental principles of Nen are Ten, Ren, Zetsu and Hatsu.
Normally, these things shouldn't have much importance in the Jujutsu Kaisen universe.
Yet, Chrollo had forgotten crucial information because of the shock linked to the incident with Suguru Geto and the memories of Meteor City.
Normally, a sorcerer needs good control of their emotions to control their cursed energy.
They also need talent to hope for a large quantity of it.
However, Chrollo remembered crucial information about himself.
His cursed energy is influenced in its nature by Nen.
His situation is a bit like Kashimo's, who has cursed energy with electrical properties.
Except that his is cursed energy with the properties of Nen itself.
Originally, his innate cursed technique is literally a Hatsu.
Which is normal, because he already knew that his power would be forcibly adapted to this reality.
But he hadn't suspected that his cursed energy would have gained properties too similar to Nen, to the point of functioning like it.
This led Chrollo to change his training program, which was supposed to focus on his control of cursed energy.
Chrollo began practicing the four fundamental principles, after watching movies.
Of course, physical training was scheduled despite his young age and pushed to the extreme.
He spends dozens of minutes releasing his Ren, hoping to increase his cursed energy reserves, and enjoys teasing Megumi thanks to Zetsu.
He also kept strict control over his Ten all day, except when Gojo Satoru came home.
Despite his remarkably rapid evolution in Ren, Zetsu, and Ten, he had struggled for weeks with his Hatsu.
He wanted to be able to fully access the powers contained inside his Bandit's Secret or Skill Hunter.
Currently, he can activate his Hatsu and use it correctly.
As for the goal he aimed for? It's almost complete.
He can already use certain Hatsu of the Brigade members, but those stored by Chrollo are more energy-consuming.
This testifies to Chrollo's own monstrous talent and the influence of an environment on a person.
Unlike the original, Johnson is not in Meteor City and has no real immediate urgency on his life.
However, the original Chrollo and his friends had to stay on their guard at all times because of mafia gangs or human traffickers controlling the landfill city.
Despite having come all this way in a few weeks, he is still not satisfied with his evolution.
"Are you really sure you're a 7-year-old kid?"
It's barely been 1 month since his arrival at the Gojo clan residence, but his progress is frightening by sorcerer world standards.
During this period, Chrollo's skinny body has changed enormously.
He remained abnormally pale, as he never left the Gojo clan domain.
He insisted a lot on taking special home courses, which wasn't really well received by Satoru.
Yet, he accepted on the condition that he would return to an educational establishment in high school.
An easily accepted agreement.
This provided him with a lot of free time to stay focused on the memories of the original Chrollo, but also on personal training.
"You know I'm not even 7 yet... it's next week," he said, between two breaths.
He points a knife at his opponent, the mountain to climb if he wants to defeat all his future rivals.
"Haha, yes you're right," the white-haired man smiles, nodding, without really taking his opponent seriously.
– Bam
A slight crack was dug by Chrollo's small foot, which had pushed too hard on the ground.
Thanks to the abnormal properties of his cursed energy similar to nen, Chrollo's physical strength is absurd.
He is still far from Killua's level at his age, but he is sure to already have strength measurable in hundreds of kilos in his small juvenile arms.
Despite this, Gojo wasn't afraid.
'This kid is really strong... and his movements...'
All of Chrollo's attacks come from his memories of Meteor City.
Every movement, attack, feint, or maneuver.
All of this was aimed at killing.
Gojo feels the killing intent emitted by Chrollo at each spar, but today is different.
'This impulse seems to be fading... Has he decided to stop seeing Suguru in front of him? Or has he simply learned to control this murderous impulse?'
Gojo was right.
Unlike the original Chrollo, he had trouble hiding his murderous intent.
After all, he wasn't really Chrollo, was he?
That's why he forced himself to visualize Suguru in front of him at each spar against Gojo.
He wanted to gain this aspect of the original Chrollo in his memory.
This inhuman side of killing naturally.
A mark belonging to formidable people like Yoriichi from KNY.
Result?
He succeeded, after a month of training using memories related to Meteor City.
A place where killing or being killed is as normal as eating stale bread.
Despite Gojo's amazement at this abnormal situation, he kept a nonchalant expression.
He grabbed Chrollo's grip, before blocking his kick aimed at his chin to finally push him back with a blow to the stomach.
"Ha..." Despite himself, Chrollo let out a groan of pain because of the air forcibly expelled from his body due to the shock.
"Oops, I got carried away haha."
"I hope there are no hard feelings."
Despite his joking and embarrassed tone, Gojo seriously observes the child getting up without crying or complaining after his blow.
"No problem... shall we continue?"
"Little glutton."
Gojo just fixed his dark glasses, before sketching a smile stranger than usual.
'No doubt about it, he really is Suguru's little brother.'
...
Finally, Chrollo's 7th birthday arrived.
He didn't really intend to celebrate this event and he didn't ask Gojo for anything, despite the special day.
He had decided to leave the Gojo clan domain, to walk around a bit and explore this world.
'I can't stay locked up forever... given Megumi and Tsumiki's reaction, I must have really worried them by staying cooped up.'
His request to go out was surprisingly well received, but it's just a bonus for Chrollo.
Of course, Satoru had him accompanied by Gojo clan staff.
"You finally decide to go out..."
After a tour in a shop extremely filled with women, who were staring at him,
Chrollo met a face he didn't want to see right now.
"Why are you making that face? I didn't mean to scare you haha, I just wanted to apologize and wish you happy birthday, little bro."