Rinto had no idea when dawn had broken.
The desk lamp had long since made his vision swim. He rubbed his eyes, got charcoal dust from his fingertips in them, and swore, "Fuck," at the gritty sting. Grabbing the bottle of cold water on the desk, he splashed his eyes twice. Icy water ran down his cheeks and dripped onto the drawings covered in iron filings, spreading a small patch of ink. He ignored it.
The piece of Starfall Iron he had ruined yesterday lay on the desk. Switching between its two attributes worked smoothly now, but after five or six consecutive switches, the metal became too hot to hold. By the end of yesterday's tests, it had blistered his fingertip, and even now, brushing it against the gauze brought a lingering ache.
He held the scrap metal, turning it over and over for a long time, muttering, "Fuck, still too hot. Heat builds up in the channels and can't escape... add cooling grooves? Too deep and they affect the flow rate; too shallow and they're useless..."
Still muttering, he grabbed a charcoal pencil and sketched on scrap paper. After a couple of strokes, he viciously crossed it out, drew again, then crossed it out again. Before long, black lines covered the page. Irritated, he tossed the pencil aside and leaned back in his chair, closing his eyes for a while. His mind was full of rapidly flowing chakra, heat following the patterns and collecting at the edges and corners. Round and round he went, unable to find a way to carry it out smoothly.
Less than two minutes later, he abruptly sat upright again, grabbed a fresh piece of Starfall Iron, and clicked it into the vise. He changed the curvature of the main channel and added several hair-thin cooling grooves along the side. His hand trembled a little as he cut. He had been awake for nearly a full day and night, and the cracks in his fingertips tugged painfully again. Gritting his teeth, he swore whenever a cut went slightly crooked. Halfway through, his hand became too numb to hold the knife. He shook it for a long time and flexed his knuckles until they cracked before continuing.
Once he finished, he took it to the steel target plate to test it. The first three switches were stable, and the temperature did not rise too quickly. But on the fifth, the moment he activated Explosion Release, residual chakra that had not been fully channeled out clogged the cooling grooves and exploded right inside them. A chunk broke off the side of the Starfall Iron. Fragments struck the back of his hand, cutting another small wound, and blood immediately seeped out.
"Fuck." He slammed the scrap metal onto the desk. Blood dripped down the back of his hand onto the steel plate, but he ignored it and stared blankly at the broken notch. After nearly ten minutes, he suddenly scoffed and cursed himself. "Fucking idiot. Robbing Peter to pay Paul."
He turned and lunged at the material rack, rummaging through it with a clatter, sending boxes and jars crashing about. After a long search, he dug out several thin copper sheets—Kabuto had tucked them in with an earlier delivery of materials, saying they conducted heat well. Rinto had glanced at them and tossed them into a corner of the rack, then forgotten all about them.
He weighed the copper sheets in his hand, then held them up against the light and examined them for a long time before sitting back down to revise the drawings. He wanted to separate the cooling structure from the main channel, but after barely a couple of strokes, it felt wrong again. The copper sheets would not fit closely enough against the Starfall Iron; if chakra seeped in, it would still explode. He tossed the pencil aside and stared at the copper sheets, his mind a noisy jumble. One moment he wondered whether he could carve the patterns into the copper, and the next whether he needed to widen the main channel. The more he thought, the more confused he became. He swore and threw the copper sheets aside too.
Two soft knocks sounded at the door. Kabuto pushed it open and poked his head inside. Seeing the mess covering the desk and floor, he lightened his footsteps further.
"Sorry to disturb you, Mr. Rinto," Kabuto said quietly. "The Cursed Seal concealment configuration you drew for Lord Orochimaru earlier—he said the parameters at one corner don't match. He wanted to ask whether you still have the draft, or whether you could check it again."
Rinto raised his head, his eyes bloodshot. It took him two seconds to register what Kabuto meant. He had casually sketched it last week and had long since forgotten it. Frowning, he rummaged through the towering pile of discarded paper on his desk, sending sheets flying. After a long search, he finally found the crumpled draft among the scrap paper at the corner of the desk, still speckled with iron filings and water stains.
"This one." He tossed the paper to Kabuto, his voice still full of irritation. "Just follow this. I marked the curve at the corner. He didn't look closely enough."
Kabuto hurriedly caught it and carefully smoothed the page. Glancing at the annotations, he quickly nodded. "Of course, of course. Sorry for the trouble." He noticed the bleeding cut on the back of Rinto's hand and the unopened gauze on the desk. He wanted to say something, but feared annoying him, so he merely set the fresh rice balls and water he had brought on the nearest corner of the desk, then quietly withdrew. As he closed the door, he heard another curse from inside, followed by the dull thud of metal hitting the desk.
Rinto did not notice what Kabuto had left at all. His mind was entirely occupied with cooling. When he had thrown the copper sheets aside, he had caught sight of a discarded draft of the senjutsu circulation configuration, and a thought had occurred to him: Could I turn the one-way channel into a small loop and let the chakra carry the heat away, instead of forcing it to dissipate outward?
But he rejected the idea as soon as it arose. A circulation structure would slow the switching speed. Reconstructing the tracking anchor points already took time; adding a loop would make the switching delay too high to use.
He irritably raked his fingers through his hair, which was as messy as a bird's nest and full of iron filings and charcoal dust. Picking up the water Kabuto had just left, he unscrewed the cap and gulped down more than half the bottle. Only after the icy water reached his stomach did his temper subside a little.
He did not rush to carve another piece. Instead, he pulled over a stack of discarded drafts and flipped through them one by one. He was not looking for inspiration, just leafing through aimlessly, coming across the Ice Release configuration that had exploded before, then the discarded draft of the Hashirama Cells' tracking anchor points. He looked at whatever came up, his mind a jumble, thinking about one thing, then another.
As he flipped through them, he suddenly stopped on one sheet. It was a diversion structure he had drawn while carving the senjutsu configuration, intended to bleed off the force of natural energy, though he had never used it. He stared at the diversion lines for a long time, muttering, "Diversion? Divert some chakra from the main channel and let it carry the heat away? No, divert too much and the power drops..."
Pencil in hand, he sketched casually in a blank space, drawing a main channel with narrow diversion grooves. These were not the static cooling grooves from before, but fine grooves that followed the chakra flow. During a switch, the grooves would adjust along with the anchor points, carrying heat away without affecting the flow rate in the main channel.
The longer he drew, the more smoothly it went. The point where he had been stuck seemed to loosen a little. But halfway through, the pencil lead snapped. He swore and bent down to find another pencil. The floor was covered with discarded paper and fragments. After feeling around for ages without finding a usable pencil, his temper flared again. He slapped the paper onto the desk, stood up, and noisily rummaged through the pencil box.
Once he found a pencil and sat back down to examine the structure he had drawn, it felt wrong again. The diversion grooves were in the wrong positions. Residue would still collect, and it would still explode. He crossed out everything he had just drawn, slumped over the desk, and stared at the blank paper without making a stroke for a long time.
Outside the window, the sky had darkened again. He did not turn on the lights, relying only on the desk lamp above him, whose battery was nearly dead. Its light grew dimmer and dimmer, but he did not notice. Holding the pencil, he unconsciously traced lines across the paper. His mind was full of chakra flow, heat buildup, and anchor-point reconstruction, all tangled together in a hopeless knot.
After who knew how long, his stomach suddenly growled fiercely, hunger leaving it painfully hollow. Only then did he remember that he had gone almost two days without eating. He glanced at the corner of the desk. The rice balls Kabuto had left that morning were still there, their plastic wrap untouched. He picked one up, unwrapped it, and bit into it. The hard rice hurt his teeth, but he did not care. He finished one in a few bites and gulped down some water, choking so badly he craned his neck.
Eating did little to revive him. After nearly two days awake, drowsiness washed over him in waves, and his eyes stung too badly to stay open. He leaned back in the chair and closed them, intending to doze for two minutes. But the instant he closed his eyes, the placement of the diversion grooves surfaced in his mind again. His eyes flew open, and he grabbed the pencil and began drawing.
After only a few strokes, it felt wrong again. Irritably tossing the pencil aside, he picked up a fresh piece of Starfall Iron, intending to carve a simplified version first and test it. But as soon as his hand touched the vise, it shook so badly he could not hold the carving knife.
He swore, "Fuck," and threw the carving knife onto the desk. Rising, he paced around the laboratory. After two circuits, he crouched on the floor and rummaged through the materials ruined in previous explosions. He picked them up one by one, examining where they had fractured and the patterns that remained, trying to find some regularity, until his hands were covered in iron filings.
After searching for a long time without finding any leads, he only felt his head growing heavier and his vision blurring further. He leaned against the wall and slid down to sit on the floor, closing his eyes and taking a breath. He had only meant to rest for a few seconds, but his eyelids grew heavy, and he fell asleep against the wall, still holding half a piece of crystal jade ruined in an explosion.
The laboratory was silent. Only the desk lamp still shone faintly, illuminating the mess covering the desk and floor, and the boxes of scrap piled high in the corner.