But Arata's genjutsu was different.
The moment he began manipulating someone's chakra, he would simultaneously convert that chakra into electrical signals and use them to interfere with the nervous system. That let the body perceive more information and send it back to him. He could then edit that feedback, filling in every missing detail inside the illusion and pushing the hallucination infinitely closer to reality.
This method of converting chakra into electrical signals was something normally found only in extremely advanced medical ninjutsu. Tsunade had used the same underlying principle to develop Nervous System Rupture, but Arata had gone down a different road, combining medical ninjutsu with genjutsu.
Inside the illusion, the victim's consciousness kept sending control signals from the brain to the rest of the body. Arata intercepted them one by one, copied them, and once he had fully grasped the neural commands governing the body, everything except the victim's brain could be ruled by his chakra. Escaping became impossible to even think about. They could not even knead chakra anymore.
In the end, the goal was total control of a person, mind and body alike.
Anyone who did not understand both genjutsu and medical ninjutsu at the highest level would not even be able to comprehend what he was doing, much less break it. It was the kind of jutsu that could kill without leaving a trace.
Of course, it was not invincible.
To cast the illusion, he first had to enter the other person's body. For now, it was strictly one-on-one. Once he controlled one person, he had no way to control a second. And no matter how realistic an illusion was, it was still an illusion. Early on, if someone disrupted their chakra, it could still be broken.
If he ran into a true expert, someone who reacted the instant they sensed anything off in their chakra, he still did not have many options. At best, he could keep burning through parts of his own body to pile debuffs on the host and make their life miserable.
And his chakra reserves were not especially large to begin with. Inside a non-Uchiha body, he could not recover at all, so his control time was very limited.
Strengths and weaknesses, then.
A strange, highly personal kind of genjutsu.
"Rustle."
Sasuke's body sat up in an unnatural posture. His hands hung limp at his sides, his shoulders drooped, his head tilted crookedly, and drool ran from the corner of his mouth.
As expected, the more intense the emotion inside the illusion, the easier it is to capture fine neural signals. I can already manage a basic level of control, Arata thought. Another three to five rounds and the jutsu should be complete.
Still, using neural signals to command a body is a real pain...
He found it genuinely tricky. Back when he had been studying and developing the jutsu, he had experimented on corpses, trying to simulate nerve signals and make dead bodies move. He had left quite an impression on the nurses at Konoha Hospital. But controlling a living person's body was obviously harder by more than one level.
There was simply too much information to process. It was not just the muscles used for movement. Skin, organs, breathing, every system in the body responded the moment a command was issued and started feeding information back. To keep Sasuke from noticing, Arata had to intercept all of it and imitate the brain's nervous system to process the data. Just making him sit up was already a headache.
This was not something a normal person could ever do.
"Good thing I'm not a person. I'm a chakra spirit."
Grumbling to himself, Arata slowly began trying to guide Sasuke's body back down again.
No need to rush it in a day or two. Slow and steady was fine. The Uchiha massacre would happen when Sasuke was seven, in his second year at the Ninja Academy. There were still close to two years left.
As for the drool running out of his mouth...
That, unfortunately, was beyond Arata's power.
---
"This is...?"
Sasuke slowly opened his eyes and stared at the clan district street, striped with moonlight and shadow.
"Genjutsu?"
But it was too real.
He pushed himself up, only for his palm to land in something thick and sticky on the ground. Blood. His nose, as though it had suddenly cleared, flooded him with the copper stench of it. Startled, he jerked violently and rolled into the moonlight, dropping into a crouch as he looked back.
Three familiar bodies lay in the shadows.
They were Uchiha ninja, men especially close to his father. They had visited the house only yesterday.
Of course it's genjutsu, Sasuke thought.
Or rather, told himself.
"Should I... go home and check?"
After hesitating again and again, he started toward the house. First slowly, then at a brisk walk, and finally at a run. Throughout the whole thing, he did not notice a single flaw. Even the sensation of his own body running felt completely real.
Is this really genjutsu... or a dream?
His childish certainty began to crack. More and more corpses appeared along the road. Clan ninja. Ordinary civilians. Familiar neighbors. Every last one of them lay collapsed in pools of blood.
Bang!
Bang bang bang!
Sasuke slammed through the half-closed front door and saw his older brother standing in the shadows, with his parents sprawled in blood at his feet.
Genjutsu! Genjutsu, genjutsu...!
His whole body shook. His chest rose and fell violently, and his ragged breathing pulled in more and more of that blood-soaked smell, each breath sharper and more real than the last.
"Gasp!"
"Sasuke?"
Sasuke's eyes snapped open. His mother was sitting beside him.
He realized he had already returned to reality. There were so many things he wanted to say, but in the end, he only parted his lips and said nothing at all.
"Sasuke..."
Mikoto looked at the single tomoe that had appeared in her son's eye and then faded just as quickly. There was no joy on her face.
She understood very well what it cost to awaken the Sharingan.
"Dinner's ready."
In the end, she said nothing else. She simply used a handkerchief to wipe the drool from the corner of his mouth. The flustered, almost adorable look on his face softened the gloom in her heart a little.
Maybe she had only imagined it?
She chose not to mention what she had seen.
Sasuke was still trapped in the aftershock of that dream, unable to pull himself free. How could genjutsu feel that real? Who had cast it on him? At home, there should not have been anyone who could just walk in and place him under an illusion.
Even as a joke, using something like that as a prank was going way too far...
He was distracted through the whole meal.
After dinner, under normal circumstances, he should have spent some time studying from his scrolls before laying out his bedding and going to sleep.
But tonight, no matter how hard he tried, he could not focus on a single word. Sitting at his desk, all he could think about was that genjutsu.
He hesitated over whether he should tell his father, tell his mother, or wait until his brother came back and tell him instead.
If it was not genjutsu at all, if it had just been a dream, then going to someone because he'd had a scary nightmare would be... embarrassing.
And if he told his brother, then his brother would definitely tell their father, and then...
More importantly, he had sworn to catch up to his brother and earn his father's approval. He absolutely refused to lower himself in his father's eyes.
After turning it over and over in his mind, Sasuke rejected the idea.
I'm an Uchiha, he told himself, clenching his fist to steel his nerves.
No matter how frightening a dream was, it could not defeat an Uchiha.
Absolutely not.
"Haaah..." He yawned again as drowsiness surged up.
For some reason, the feeling was strangely familiar. Sleep swallowed his mind almost at once. Moving like a machine, he laid out his bedding, slid under the blanket, and the moment his eyelids touched, his consciousness began to sink... and sink... and sink.
When he opened his eyes again, that familiar smell of blood rushed into his nose.
It seemed that tonight, the nightmare had arrived right on schedule once more.