The morning after, Rei felt like a new person.
Learning the reverse technique hadn't just helped with the physical wounds — it kept his mind clear with a sharpness he hadn't felt in a long time. There was something about positive energy circulating through his body that washed away the background noise, that accumulated exhaustion you stop noticing because it becomes constant.
With that clarity, Rei began to theorize.
If he used Paradox alongside the reverse technique, the healing efficiency didn't just increase — the energy cost went down. The logic was the same as any paradox he created: instead of generating positive energy from scratch, he could create the state where cursed energy was simultaneously negative and positive at the same time. Two opposing states coexisting — Paradox doing what it always did, but applied to his own biology.
The principle was similar to destructive interference in physics — two opposing waves that, when superimposed, don't cancel each other out but instead create a third state. In this case, negative cursed energy and its positive inverse coexisting in superposition produced a state where the body didn't need to repair the damage because simultaneously the damage existed and didn't exist. The paradox naturally collapsed toward the state of non-existence of the wound, which was the path of least resistance. In practical terms — the healing happened almost on its own, at a fraction of the normal energy cost.
Rei tested it with a small cut on his finger. It worked.
He stared at it for a moment with the expression of someone who had just confirmed a hypothesis they had been hoping was correct. Then he filed away the results mentally and got on with his day.
There was a knock at the door.
He opened it to find the already familiar face of Gojo Satoru. "Gojo-sensei," Rei said, nodding in greeting. Even though he wasn't as tense as he'd been the first few times, something in him still stiffened slightly whenever the white-haired man came around — not exactly fear, but the specific discomfort of someone who knows they're being analyzed in far more detail than it looks.
Before even saying hello, the first thing Gojo noticed were the traces of positive energy still drifting through the air of the room. He couldn't help but smile to himself.
The current generation was producing talents that defied all logic. Okkotsu Yuta had mastered the reverse technique in roughly a month — and Yuta was an extraordinary case for his own reasons. Kagami Rei had been at the school for two weeks. And that wasn't even counting Megumi, who had the potential to pull it off whenever he decided to seriously try.
It was a good time to be a teacher, if that was even the right word for it.
"You have a mission," Gojo said, without mentioning the other thing.
Rei looked at him. It was his first formal mission — student sorcerers didn't usually go alone, but the staff was stretched thin and Megumi had his own assignment, a special-grade cursed object that required separate attention. Gojo had personally handed him the briefing paper, which was in itself unusual enough for Rei to make a mental note.
A grade-two curse was estimated to have been lurking near a highway on the outskirts of the city. Several cars had been involved in accidents attributable to the curse. There was no detailed physical description, but the word-of-mouth legends about roadside ghosts pointed to a freshly born spirit.
The area where the accidents had been occurring had been closed off under the pretense of road construction to keep civilians from continuing to pass through.
Before leaving, Rei said goodbye to Gojo and to Megumi, who was heading off in the opposite direction with that quiet focus he carried whenever something mattered to him, even if he'd never say so.
"Don't prioritize the mission over your life," Gojo told him as Rei was already walking toward the car. "I can't afford to lose students this soon."
Rei didn't answer, but nodded without turning around.
The ride was silent from start to finish.
Rei wasn't the kind of person who started conversations, and the assistant assigned to him — a middle-aged man with the face of someone who had seen too many missions to find small talk necessary — wasn't either. They shared the quiet of the car with the ease of two people who don't know each other but don't bother each other either.
When they reached the area, the assistant spoke for the first time since they'd left the school.
"I'll set the curtain. Good luck."
Rei gave a slight nod and started walking toward where the curse was supposed to be. Behind him, the assistant recited the incantation and the sky was swallowed by darkness.
Most curses are born from humans — beings spawned from their deepest fears, their envy, their rage, the negative emotions that build up with nowhere to go. There were cases like Kagami Souta, people who died carrying a resentment so profound that the possibility of being reborn as a curse was real, if rare.
But humans weren't the only creatures in the world that felt.
In life, Miyu had been a dog belonging to a family in Tokyo. Her earliest memory was probably the moment she was adopted by a young couple just starting their life together. For years she protected their home with everything she had — to her, her owners weren't simply the people who took care of her. They were the meaning of her existence.
Until the couple decided to have children.
It wasn't an unusual case. It happened everywhere, not just in Japan — when kids came along, pets sometimes became a problem to be dealt with. Miyu was abandoned on a highway at the edge of the city.
She never understood what she had done wrong. She thought it was a walk like any other, and she was happy to be in the car with her owners — but when they let her out and she watched them drive away, she understood it would be the last time. She tried to reach them. She ran down the highway at full speed, chasing the car as it grew smaller and smaller in the distance, but she couldn't catch it.
A truck hit her. Nobody cared. Her body was left on the side of the road.
She died carrying a grief so immense, so deep, that she was reborn as a cursed spirit. And even after being reborn, Miyu kept doing the last thing she had done in life — chasing cars.
Rei knew none of this when he arrived at the origin point.
The first thing he noticed was that something felt off. The curses he had faced until now had that specifically revolting quality, a dark and aggressive density you could feel on your skin before you ever saw them. This was different.
It was sadness. Not his own — or at least not entirely. It was a sadness coming from outside, seeping slowly inward like water finding the cracks in a wall. Rei found himself involuntarily cycling through the hardest moments of his life — his father, the Sunday visits, the night of the knife, everything that could have been different if things had been different, if he had been different.
He stopped.
He noticed what was happening with the detached clarity of someone accustomed to watching himself from the outside. The cursed energy reinforcing his body had partially protected him — the civilians who drove through this road had no such protection, which explained the accidents. The curse wasn't attacking them directly. It was simply pulling them under a sadness deep enough to make them stop paying attention to what was in front of them.
He let out a long breath to clear his head and settled into a fighting stance.
Miyu's cursed spirit emerged from between the trees.
It was enormous — roughly three meters, maybe more. It still held the shape of a dog in a recognizable way, but distorted at the edges, like an image someone had stretched too far. Its face was disfigured, the eyes looked hollow, and the mouth twisted into something that could have been a smile or could have simply been what pain looks like when it lasts too long.
It didn't attack.
It didn't move. It only looked at him.
"Why aren't you attacking me?" Rei asked, in that direct, slightly awkward tone he used when he wasn't sure what the right protocol was. He wasn't entirely certain the curse could understand him.
The curse tilted its head — that specific, unmistakably canine gesture — then looked to one side and began to walk.
Rei took a moment to decide. Then he followed.
They didn't walk far. The curse stopped beside what appeared to be remains — what was left of a small animal, worn down by time and sun until there was little more than fragments.
"That's you," Rei said quietly.
The curse didn't respond. Rei hadn't expected it to.
He stood looking at the remains for a moment. The Jujutsu world wasn't always black and white — he had thought that before, in the abstract. Now he was seeing it head-on. There was nothing to fight here. There was no enemy. There was only something that hadn't finished happening.
Even though he had an easy stomach for most things, Rei knelt down and began to dig with his hands. Without saying anything. Without explaining. It was simply what needed to be done.
The curse watched him in silence throughout.
When he finished, Rei stayed for a moment with his hands pressed together in front of the buried remains. He wasn't a believer in any formal sense — he had no religion, no specific god to address. He simply wished, with the same plainness with which you wish for anything that matters, that this dog could rest.
He turned around.
Miyu's eyes were on him — that enormous, bottomless sadness that had been radiating since he arrived, and that Rei now felt in a completely different way than he had before. Not as a threat. As what it was.
"I don't know what happened to you," Rei said. "I don't know your circumstances either."
He extended his hand. He pressed his index and middle fingers together, keeping the others closed. Cursed energy and its inverse began to circulate simultaneously — creating the impossible state where both coexisted, where existence and non-existence were equally true at the same time.
A flash washed over the curse completely.
"But I know you never hurt anyone out of hatred."
Aporia — the technique born from combining Paradox with its inverse — was at its core an existence paradox applied gently: reality collapsing in on itself. Anything touched by that energy entered a state of simultaneous existence and non-existence, and from there collapsed toward the only state where the contradiction resolved — the absence of pain, the absence of sadness, silence.
A painless death. Peaceful. Right.
"You were a good dog."
When the energy faded, there was simply silence.
The curtain dissolved slowly, letting the ordinary sky return over the empty road. Rei walked back toward where the assistant was waiting, wiping his hands on his trousers. There was something in his chest he couldn't quite name — not exactly satisfaction, not exactly sadness. It felt more like the feeling of having done something worth doing, even if no one would ever know.
Maybe the Jujutsu world sometimes needed more than just hitting hard.