He built a routine because routines were simple and simple was what he needed when everything else about his situation was the opposite.
Mornings were physical.
A park four blocks from the apartment had a running track and public exercise bars, the metal pull-up stations that Japanese parks installed everywhere and that were always either completely empty or occupied by a single old man exercising with unsettling intensity.
At six AM, it was empty. Shin ran, did pull-ups, did dips, did circuits until his muscles burned, and while he worked he fed cursed energy into specific muscle groups to test the limits of reinforcement.
The results were immediate.
A pull-up that required moderate effort became nothing. His body rose and fell on the bar like gravity was a suggestion rather than a law, smooth and mechanical and precise. When he pushed the reinforcement higher, channeling more energy into his grip, the metal bar groaned under his fingers and began to deform.
He eased off. Breaking public property was the kind of thing people noticed.
But the data was useful. Reinforcement scaled directly with the energy applied, and his reserves were deep enough that even heavy output barely registered as a drain. If he reinforced his entire body simultaneously, he'd be something beyond human. Not Gojo-level, Gojo's power came from technique rather than raw physicality, but comfortably above most grade one sorcerers in pure physical terms.
And he still didn't have a technique.
That part would come. Or it wouldn't. Either way, the body needed to be ready.
By the end of the first week, the routine had sharpened him. Movements were crisper, recovery times shorter. The body the system had given him responded to training the way good steel responds to a whetstone, and Shin used every morning to grind it a little finer.
---
Afternoons were for hunting.
He started with the industrial strip along the river, where warehouses sat empty after dark and the ambient cursed energy was thick enough to sustain a steady population of low-grade curses.
Grade fours were nothing. One reinforced strike and they came apart like wet tissue, barely worth the effort of tracking them down. He moved to grade threes within days, and these were better. Faster, tougher, some of them with abilities that required actual thought to counter.
One could extend its limbs like whips. Another secreted a corrosive substance that ate through concrete. A third was fast enough that he had to reinforce his legs to full capacity just to keep pace with it.
He killed them all. Not elegantly, not with the polished efficiency of a trained sorcerer, but with the blunt, methodical persistence of someone who treated each fight as a lesson and each injury as tuition.
And there were injuries. Bruises, mostly. A gash across his forearm from the fast one that took two days to close. A burn on his palm from the corrosive one that he'd grabbed without thinking.
He catalogued them and moved on.
---
On the ninth night, he found something that actually scared the empty space where his survival instinct used to be.
Loading bay of a shuttered packaging plant in the industrial district. He'd felt it before he saw it, a pressure against his senses that was qualitatively different from anything he'd encountered so far. Heavier. Denser. The grade threes felt like insects bumping against his awareness. This felt like a hand pressing against his chest.
It was on the ceiling.
Three meters across, flattened against the corrugated metal like a stain, pulsing with slow contractions. Dark, semi-liquid, featureless except for the dozens of mouths scattered across its surface, lipless and irregular, opening and closing in silent rhythms that had nothing to do with breathing or speaking or any function mouths were supposed to serve.
Grade two.
It knew he was there. He could feel its attention, cold and calculating, nothing like the mindless hunger of the weaker spirits. This thing was thinking.
It dropped.
Fast. Peeling off the ceiling in one fluid motion, unfolding as it fell into something approximately humanoid, arms and legs and a central mass all composed of that same dark, glistening substance.
Shin sidestepped. The curse hit the concrete where he'd been standing and cracked it. He drove a reinforced fist into its torso before it could recover, channeling energy through the contact point.
The impact blew a hole the size of a basketball through its midsection.
The hole closed in three seconds. Dark substance flowing inward from the edges, filling the gap like water finding its level. The curse turned toward him and screamed from every mouth at once, a wet, layered sound that echoed off the metal walls.
Regeneration. The body's expendable. The mouths are the core.
It attacked with extended limbs, arms stretching past their natural length like pulled rubber, whipping through the air with an unpredictability that made them harder to track than a straight charge. One caught his left shoulder before he could fully evade.
The contact was wrong. Not painful in the way a punch is painful but wrong in a deeper way, a jolt of foreign cursed energy that felt like corruption pushing into his tissue. His own energy rejected it, expelled it, but the bruise it left went all the way to the bone.
He grabbed the extended arm before it retracted. His reinforced grip locked down on the limb like a vice, and he pulled.
The curse came toward him whether it wanted to or not, dragged off balance by a force it couldn't match. Shin met it with his free hand, palm flat against the cluster of mouths on its chest.
He didn't strike. He flooded.
Cursed energy pouring through the openings in a volume the curse's own energy couldn't resist, filling its internal structure the way a river fills a bottle, and then detonating everything from within.
It came apart all at once. Body losing coherence, substance evaporating, leaving nothing but cracks in the floor and a faint residual energy that would be gone by morning.
Shin stood in the empty loading bay breathing harder than he liked to admit.
His shoulder throbbed. His reserves had dipped, not dangerously, but enough to feel the difference. And the fight had lasted maybe twenty seconds.
Twenty seconds against a grade two, decided by overwhelming force rather than skill.
Against anything smarter, anything with a real technique, force alone wouldn't be enough.
He needed something more.
---
On the fourteenth day, it found him.
He hadn't been searching. That was the part that mattered, that the thing he needed most arrived only when he stopped looking for anything at all.
Evening. His apartment. Light fading outside, room dim. He was sitting on the tatami with his back against the wall, awareness drifting through the internal landscape of his own energy in the aimless way that had become habit during the quiet hours.
Not meditating. Not training. Just existing, his mind empty the way it had been empty for years, the silence of a room where no one lives.
Thinking about nothing.
And beneath the currents, beneath the core, beneath everything he'd mapped and trained and refined over fourteen days, he touched something he'd never felt before.
It wasn't a void. It wasn't power. It wasn't anything he had a framework for.
It felt like a mirror.
Not visually. The quality of it was reflective, sitting at the center of his energy, and it was turned inward, pointed at him, and before he could examine it further—
The apartment was gone.
---
He was standing on water.
A lake. Vast, perfectly still, stretching to a horizon that didn't exist because the sky and the water's surface were the same color. Pale, luminous white. Not quite white. The color of silence, if silence had a color. The two planes, water below and sky above, merged at some impossible distance into a seamless unity, and there was no way to tell where one ended and the other began.
No wind. No sound. No movement except the faint ripples spreading from where his feet rested on the surface, which held his weight like glass.
He looked down. His reflection stared back, clear and perfect and undistorted, rendered with a fidelity that went beyond physical accuracy into something more honest than any mirror he'd ever looked into.
And beneath the reflection, beneath the surface, there was depth. Not the depth of water measured in meters but a different depth entirely. Vast, still, empty.
This was him.
This endless calm. This silence. This featureless expanse of nothing pretending to be something. The mirror at the core of his technique had turned inward and reflected his nature, and his nature was a lake with no bottom under a sky with no end, both the same color because they were both the same thing.
Mirror Realm.
The words arrived without being taught, recognized rather than learned. He'd always known them. He was only now finding where they fit.
He stood on the still water and understood.
This was his cursed technique. Not a Domain Expansion, not yet, but the seed of one. A space that existed inside his energy, shaped by his nature, built from whatever truth the mirror found when it looked at something.
When it looked at him, it found this: calm. Emptiness. A peace that wasn't peace but was the absence of anything to disturb.
When it looked at someone else—
He understood the principle even if he hadn't tested it.
Pull someone into the Mirror Realm and the space would reshape around their nature. Their truth, stripped of every lie they told themselves, every mask they wore, every justification they hid behind. A person built on rage would see fire. A person drowning in grief would see rain that never ended. A person with something monstrous inside them would see exactly what that monster looked like when it had nowhere to hide.
And while they stood in a landscape made from their own exposed soul, Shin would be standing on calm water under a white sky, at home in the nothing, undisturbed and undisturbable, fighting on ground that couldn't unsettle him because it was him.
The combat applications stacked themselves in his mind without effort. The psychological disruption of forcing someone to confront their own nature. The potential to reflect cursed techniques, turn an opponent's energy against them. The home-field advantage of a space built from his own emptiness.
He stood on the water for a long time.
Then the realm folded, silent and clean, depositing him on the tatami floor as if he'd never left.
His reserves had dropped significantly. More than the grade two fight. Maintaining the realm was expensive, and pulling someone else into it would cost even more.
But it was his. A technique born from a man with nothing inside him except a mirror that showed everyone else what they really were.
Shin closed his eyes and leaned his head back against the wall.
Seventeen days remaining.