The door did not break all at once.
It complained first—wood fibers screaming in slow motion—then the lock gave with a metallic snap that sounded too clean to be natural. The candle flames bent toward the crack like they wanted to escape.
Ren's hand went to the knife at his belt.
"Don't," Aoi said.
It wasn't a plea. It was a command dressed as a whisper.
Another impact hit the door. The cheap wood bowed inward. A line of darkness widened, and with it came the smell of wet leather, cold steel, and something else—ink that wasn't ink. A mechanical ticking crawled into the room, delicate as a spider's legs.
Collectors.
Ren's throat tightened. "You said repeat after me. Repeat what?"
Aoi's fingers were still around his wrist. The oathmark on both of them pulsed, black lines brightening as if the skin underneath had become paper and something was trying to write through it.
"A short vow," Aoi said, eyes fixed on the door as if she could see the future in the splintering grain. "Simple. Defensive. The kind that doesn't try to change the world—only the rules of one room."
Ren pulled against her grip, more reflex than intention. "And the price?"
Aoi's mouth tightened. For a heartbeat, her composure cracked enough to show teeth behind it. "Less than being harvested."
The door exploded inward.
Wood shards sprayed across the room like thrown knives. A hooded figure filled the doorway—broad shoulders, mask lacquered white, the shape of a crescent etched into its forehead. Behind him, two more shadows. And behind them, the hallway fogged with a dark, crawling mist that smelled like iron filings and old vows.
Ren moved.
He threw his weight sideways, pulling Aoi with him as the first intruder lunged. Steel flashed—short sword, practical, ugly. Ren barely avoided it. The blade bit into the table, jolting the iron basin so hard it rang like a bell.
The oathmark on Ren's wrist burned.
In that flash of pain, he understood something he hadn't understood in the alley: the Ledger wasn't the only thing listening.
The room was listening too.
Aoi yanked him behind the shelves. Her other hand slapped the wall like she was sealing a letter. Ink bloomed beneath her palm—thin, clean lines that spread along the plaster in precise angles, forming a lattice that caught the candlelight and held it.
"Say it exactly," she murmured. "No improvising."
Ren's heart hammered loud enough to be an oath.
The intruder tore the blade free and turned toward them, movements too controlled for a street thug. He didn't speak. Collectors rarely wasted language out loud. Their promises were written in mechanisms.
The ticking grew closer.
From the hallway, something rolled into view—a brass sphere the size of a skull, covered in tiny joints and engraved words. It moved on its own with patient certainty, rotating as it advanced. With every rotation, the room's air seemed to tighten, like a rope being pulled.
Ren felt it in his teeth.
The sphere's engravings glowed faintly.
Names.
Ren's stomach dropped. "That's the engine?"
"Yes," Aoi said. "And it's hungry. Ren—look at me."
He did, because her voice made the act of disobedience feel like stepping off a roof.
Aoi's eyes were not cold anymore. They were sharp with urgency. "You're going to bind the space between you and the door. Not forever. Not heroic. Just long enough to breathe."
"With what words?"
Aoi inhaled once, like she was about to dive underwater.
Then she spoke, slow and clean, each syllable placed as if she was laying tiles.
"I vow," she said. "On ink and breath."
Ren heard it and felt it try to grab hold of him—language with hooks.
"Repeat," Aoi ordered.
The first Collector stepped closer, sword angled low. His mask reflected candlelight without warmth.
Ren's mouth was dry. The Ledger under his coat pulsed in time with his heart.
He swallowed and repeated, "I vow."
The oathmark flared.
A thread of black ink rose from his wrist like smoke pulled backward, but it didn't drift. It stretched, thin as hair, connecting him to Aoi's hand on the wall.
"On ink and breath," Ren said, voice catching on the last consonant.
For a heartbeat, the air went still.
Then the promise tried to complete itself.
Aoi spoke again, "That no blade may cross this line—"
Ren echoed her, "That no blade may cross this line—"
The Collector lunged.
The sword tip struck something invisible in midair and screamed.
Not metal-on-metal.
Metal-on-rule.
The blade shuddered like it had hit stone. Sparks of black light skipped along its edge. The Collector jerked backward, surprised enough to be human for half a second.
The brass sphere clicked, faster.
The engine's engravings brightened.
Ren felt pressure behind his eyes, as if the vow had decided his skull was collateral.
"—without paying in blood," Aoi finished.
Ren's tongue stumbled. Blood. The word tasted dangerous, messy, too big. He wanted to change it, soften it, make it safer.
But Aoi's grip crushed his wrist.
"Exactly," she hissed.
Ren forced it out. "Without paying in blood."
Ink snapped into place.
A line appeared.
Not on the floor.
In the air itself—a thin, shimmering seam that cut the room from the broken doorway like a surgical incision. The candle flames leaned away from it. Dust refused to cross it.
The Collector tried again, more careful this time, sword advancing by inches.
The moment the tip touched the seam, the line drank.
A bead of blood formed on the Collector's gloved hand, seeping through leather as if the oath had found skin beneath the mask without asking permission. He recoiled, hissing through teeth Ren couldn't see.
Ren's knees almost buckled.
The Tax came like winter.
Not pain—pain was honest. This was theft.
Something cold and clean slid behind his eyes and pulled.
Ren blinked hard. The shelves blurred. Aoi's face became a shape, then a person again.
He grabbed at his own mind the way a drowning man grabbed at air.
And for an instant, he couldn't remember the taste of rice.
It was absurd—small, domestic, harmless. But the absence made his throat tighten with panic. A lifetime of simple mornings—steam, salt, the comfort of cheap food—gone like someone had erased a line from a page.
Ren swallowed nothing. "What—"
"Don't fight it," Aoi said quickly, voice low. "If you claw at the hole, it widens. Let it pass through you."
"That's easy for you to say," Ren rasped.
"No," Aoi said. "It isn't."
Her eyes flicked down to her own wrist. The oathmark there was burning too, though it seemed steadier on her skin, more accustomed.
Ren realized, with a jolt of sick admiration, that she had been paying this kind of price for years.
The Collector's engine rolled forward, ignoring the barrier like it was an inconvenience rather than a wall.
The brass sphere didn't have a blade.
It had words.
As it approached the seam, the engravings on its surface shifted—letters rearranging themselves with mechanical grace. The light deepened from brass-gold to ink-black.
The ticking became a chant.
Ren felt something inside him answer it.
The oathmark on his wrist pulsed hard.
Aoi's head snapped up. "It's trying to read you."
"Then stop it," Ren hissed.
"I can't stop it," Aoi said, and the admission sounded like a blade drawn halfway. "Not alone."
The Collector with the sword stepped back, letting the engine take the front. Another shadow behind him raised a hand, and Ren saw a thin chain of paper talismans unspooling like ribbon, each stamped with a name that Ren's eyes refused to hold.
Vow-tech.
Ren's instincts screamed at him to run.
But the barrier was between them and the only exit, and the engine was already close enough that Ren could hear the soft click of its joints, patient, inevitable.
"What do I do?" Ren asked, hating how the words sounded like surrender.
Aoi's fingers tightened on the wall, ink-lattice holding. "You keep the vow alive. And you don't let it touch the seam."
Ren stared at the line in the air.
He could feel it, now—not as an object, but as a decision. A rule that existed because he and Aoi had said it did.
He understood the danger in a way his body understood hunger: if the rule broke, the Tax would not just take a memory.
It would take the part of him that made him Ren.
The engine rolled closer and pressed against the seam.
The line shuddered.
Ren's teeth clenched. He could feel the vow straining, like a rope under too much weight. The Oath Tax threatened behind his eyes, waiting to collect interest.
"Hold," Ren whispered.
The word wasn't part of the vow.
But the room listened anyway.
The seam steadied for a second.
Then the brass sphere clicked—and a needle-thin stylus unfolded from its underside, ink-black metal glinting. The tip touched the seam with delicate curiosity.
The line screamed again, but quieter this time. Like it was losing.
Aoi's breathing hitched. "Ren—if it writes on the line, it can rewrite the vow."
Ren's hand went to his coat pocket, to the warm wrong weight of the Ledger.
The artifact pulsed like it knew its name was being spoken.
Ren's fingertips brushed leather, then the edge of paper inside.
The moment he touched it, the oathmark on his wrist flared so hard it felt like flame.
He heard ink moving.
Not in the room.
Inside the Ledger.
Ren pulled it out.
The book looked ordinary in candlelight—black cover, no title, no ornament. But as it surfaced into the air, the candle flames trembled like they recognized a predator.
"No," Aoi breathed.
Ren glanced at her. "No what?"
"Don't open it," she said, and now her voice had fear in it, raw and immediate. "You don't know what page it will choose."
The engine's stylus pressed harder.
The seam buckled.
Ren's vision tunneled. His pulse became a hammer. He could feel the Tax sharpening its blade in the dark space behind his eyes.
He made a decision.
Ren flipped the Ledger open.
The pages were blank.
For exactly one heartbeat.
Then black ink flooded the paper like a spilled confession, forming characters that twisted into words Ren could read without understanding how.
They weren't his.
They weren't Aoi's.
They were the vow itself, written as a sentence that felt like a trap.
Ren didn't have time to parse it.
The engine's stylus scraped against the seam, and the line began to fray, as if someone was erasing it with sand.
"Ren!" Aoi's voice cracked. "Close it—"
Too late.
The Ledger pulsed.
A thread of ink shot from the open page to the seam in the air, stitching itself into the vow like a parasite claiming a host. The room went cold. The candle flames shrank. Even the rain outside seemed to hesitate.
Ren's breath caught.
The Tax came down like a knife.
Something in him tore loose—clean, surgical, final.
Ren gasped and staggered, gripping the Ledger so hard his knuckles went white. His mind tried to hold onto whatever was being taken, but his thoughts slid off it like water off oil.
He lost something important.
He didn't know what it was.
That was the horror of it.
The seam brightened, ink thickening along its edge, as if the vow had been reinforced—rewritten into a harsher rule.
The Collector's engine paused, stylus still extended.
For the first time, the ticking stuttered like uncertainty.
Ren looked at the barrier, at the ink that wasn't Aoi's lattice and wasn't his own thread, but something older, darker.
Aoi's eyes were wide now, shock pulling her control apart. "What did you do?"
Ren swallowed, trying to find an answer.
Outside the barrier, the Collector with the sword stepped back, as if he'd just felt the room change allegiance.
The brass sphere clicked again, slower.
Then it began to hum.
Not ticking.
Humming—low and resonant, like a choir trapped in metal.
The oathmark on Ren's wrist burned.
Not with heat.
With smoke.
Black vapor seeped from the lines on his skin, curling upward in thin strands. It didn't drift randomly—it reached toward the engine like a living thing recognizing a threat.
Ren stared, throat tight. "Aoi…?"
Aoi didn't answer.
She stared at the smoke and the way it bent the candlelight, her expression turning into something Ren didn't want to name.
Recognition.
Outside the barrier, the Collector's engine hummed louder.
And the smoke from Ren's oathmark thickened, curling into the air like a question the room couldn't refuse.