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Kaeya is three identities deep when he takes his seat.
He has stood in worse rooms - interrogation cells with blood still warm on the floor, taverns where men bragged about things that should never be done to another person, frostbitten camps where survival meant deciding who didn’t make it through the night.
This room is worse because it is civilized.
The auction floor is arranged like a theater - tiered seating, velvet drapes, low amber lighting meant to flatter both the merchandise and the men bidding on it. No chains in sight. No cages. Just attendants in crisp gloves and a podium where lots are introduced with the careful diction of a wine tasting.
He blends easily. Silk coat, relaxed posture, a bored curl to his mouth. A man with money and curiosity but no conscience - an identity he slips into with practiced ease.
The auctioneer doesn’t greet the audience. He simply opens a ledger and begins in an expressionless voice. “Lot one. Special research notes on the effects of Kuuvahki on wildlife…”
Numbers follow, data, value.
“... Lot Seven,” the auctioneer announces. “Previously restricted research asset. Condition noted in the ledger.”
Not subject. Not person.
Asset.
Kaeya lets his gaze drift, like he isn’t listening too closely.
The attendant opens a lacquered case. Inside was a delusion housing, dismantled. Its core has been removed.
“Field-tested over prolonged exposure,” the auctioneer continues. “Yield exceeded projections by forty-two percent prior to degradation.”
A murmur ripples through the crowd. Interest, not concern.
Kaeya’s fingers tighten imperceptibly around the stem of his glass.
Another lot follows. Notes projected briefly onto a screen - sanitized summaries, stripped of anything resembling humanity.
Neurological resilience observed beyond expected parameters.
Subject maintained combat functionality despite progressive failure indicators.
Compliance achieved through conditioning rather than restraint.
Conditioning.
He smiles faintly when someone nearby mutters approval. Plays the role. Makes a mental note of faces, insignias, accents.
Then-
“Supplementary documentation available to verified buyers,” the auctioneer adds. “Including field recovery reports from Mondstadt operations.”
Kaeya’s breath catches.
Mondstadt operations.
That narrows the list uncomfortably.
He reminds himself this isn’t proof of anything. The Fatui have touched nations all over the continent. Mondstadt is not unique. He forces his shoulders to stay loose, his expression mildly amused.
Still, his attention sharpens.
The next display is not a device. It’s a ledger.
Thick, bound in dark leather, its spine worn soft with handling. The attendant turns it to show the audience a page filled with neat, compact handwriting.
“Operator notes,” the auctioneer says. “Unusually detailed. Cross-referenced with physiological data. Valuable for replication purposes.”
Kaeya knows that handwriting intimately.
He's seen it stacked on Jean's desk, rolled parchments, ledgers - clipped, precise, disciplined to the point of severity.
He doesn’t breathe for several heartbeats.
A bidder raises a hand. “Why is the asset no longer active?”
. “Instability," the auctioneer replies. "Structural and cognitive. Returns diminished beyond acceptable margins.”
Another voice: “Termination?”
A polite chuckle. “No. Asset escaped containment during a third-party incident. Recovery deemed inefficient.”
Inefficient.
Kaeya’s vision narrows.
Escaped containment.
His mind supplies images without permission -Diluc returning home half-dead, feverish, shaking with injuries that never quite made sense. Adelinde’s hands bloodied from tending wounds she refused to describe. The way Diluc flinched at certain smells, phrases, anyone getting too close.
He swallows and lifts his glass, masking the movement.
Someone else asks, “If recovery were attempted now?”
There’s a pause. A deliberate one.
“Reacquisition remains theoretically possible,” the auctioneer says. “However, projections suggest limited viability. Asset degradation would likely accelerate under renewed exposure.”
Kaeya feels ice run through his veins.
Limited viability.
Accelerate degradation.
He thinks of Diluc’s quiet certainty when he speaks of his past - what little he allows himself to say. I’m not useful to them anymore.
At the time, Kaeya had heard bitterness. Resignation.
Now he hears something else.
Assessment.
The gavel comes down.
The lot is temporarily withdrawn. Deferred pending verification. The crowd shifts, already moving on, appetite unsated but patient.
Kaeya stays seated for a moment longer than necessary, forcing his pulse to slow.
He has what he came for. Too much of it.
When he finally rises, it’s with the easy grace of a man who has grown bored. He chats lightly with another bidder on the way out, offers a wry comment about the inefficiency of modern research ethics.
Inside, something is unraveling.
Because if this is Diluc - and Kaeya is almost certain it is - then the worst part isn’t what was done to him.
It’s that there are people in this room who would do it again if they thought there was anything left to take.
And Kaeya has just learned exactly how close that line still is.
Kaeya does not confront Diluc.
He watches.
Diluc moves through the manor with the same controlled efficiency he always has. Straight-backed, precise. No limp, though Kaeya notices the way he favors his left side when he thinks no one is looking.
Adelinde presses a cup of something bitter into his hands. Diluc pauses - weighing the effort of refusal - then drinks.
Kaeya files that away. Diluc used to argue.
At breakfast, Diluc eats sparingly. Nothing unusual, but now Kaeya notices the pattern - measured bites, evenly spaced, as if intake must be justified.
The teacup rattles faintly against the saucer. Diluc stills it with two fingers.
A tremor. Brief. Contained.
Neurological resilience observed beyond expected parameters.
Kaeya keeps his smile easy. Talks about nothing.
Later, in the study, Diluc stands too close to the window. The winter light is sharp, glaring off the glass. Kaeya watches him angle his body away from it by degrees, not enough to be obvious, just enough to ease something tightening behind his eyes.
Photosensitivity.
Accelerated degradation under renewed exposure.
The words echo, unwanted.
When Adelinde asks if he slept, Diluc answers, “Enough.”
Not well. Not soundly.
Enough.
His hand curls briefly against the edge of the desk when he thinks no one sees. The knuckles blanch, then relax. Pain, grounding, or habit - Kaeya can’t tell which, and that uncertainty gnaws at him.
During training, Diluc moves like himself.
The same clean strikes. The same ruthless efficiency. But Kaeya sees the micro-adjustments now - the way Diluc avoids overextending, how he ends exchanges faster than he used to, prioritizing conclusion over flourish.
Energy conservation.
Field-tested over prolonged exposure.
When a swing goes wide - barely - Diluc’s jaw tightens. Not just frustration. Assessment. As if he’s recalculating something invisible.
Kaeya’s chest aches.
He remembers a dozen moments that didn’t matter at the time. Diluc leaving rooms without explanation. Standing very still after fights. The way he sometimes goes silent when Kaeya mentions the Fatui - not anger, not grief.
Accounting. How much is left. What can still be spent.
That night, Kaeya passes Diluc’s door and pauses there briefly, leaning against the opposite wall, out of sight, and closes his eyes. He thinks of the ledger. The handwriting. The word degradation, written by people who never had to see what that looked like in a human body.
Limited viability, the auctioneer had said.
Kaeya presses his fingers into his palm until it hurts.
Because now he knows what that means.
It means Diluc has been living as if his life is a resource already partially spent - already written off by someone else.
And Kaeya smiled through it. Not anymore.
Kaeya doesn't mean to say it. Doesn't even realize he has until it’s already hanging in the air between them.
“…which is why the Knights are concerned about any potential reacquisition attempts.”
Diluc stops.
Not metaphorically. Physically.
His hand is still on the back of the chair. Fingers curled. The rest of him goes very, very still.
Kaeya falters mid-step.
“Diluc?”
No response.
Diluc can hear him. He knows that much. The sound reaches him, distant but intact, like something shouted down a long corridor. What doesn’t follow is the part of him that answers.
The room has narrowed, compressed.
Reacquisition isn’t panic. It's conclusion.
They wouldn’t stop.
They wouldn’t wait.
They wouldn’t care if he came apart.
His chest tightens, just enough that breathing becomes something he has to remember how to do.
Kaeya takes a step closer, slower now.
“Hey,” he says, gentler. “That’s not-”
Diluc’s fingers twitch.
That’s the first sign Kaeya gets that something is wrong in a way he doesn’t yet understand.
Diluc forces air into his lungs. It feels wrong. His vision blurs at the edges, not from tears but from the effort of staying here.
“They won’t,” he says finally.
The words come out flat.
“They won’t what?”
Diluc swallows.
“If they came back,” he says, eyes fixed on nothing at all, “they wouldn’t stop when it failed.”
Kaeya’s stomach drops.
Failed.
Not resisted.
Failed.
“They wouldn’t allow recovery,” Diluc continues, voice quiet, precise. “Or degradation. Or time.”
He exhales shallowly.
“There wouldn’t be enough left,” he says, almost clinically. “Not to… come back from.”
Silence. Not the comfortable kind. The kind that presses.
Kaeya feels it then - fear of being finished with.
“Diluc,” he says carefully, “no one is taking you.”
Diluc doesn’t respond. He can’t. Because the part of him that evaluates danger has already moved past whether and arrived on what remains afterward.
Kaeya adjusts.
“No plans,” he says. “No attempts. No movement.”
He keeps his distance. Doesn’t touch. Doesn’t ask for eye contact.
“You’re here,” he adds. “In Mondstadt. With me.”
Diluc’s grip on the chair loosens by a fraction.
Breathe in, then out.
It takes a long moment before he nods.
“I know,” he says.
But his voice hasn’t fully come back yet.
Kaeya watches him carefully after that - not hovering, not leaving. Just… there. Alert to the cost of that single phrase.
Later, Diluc will hate that it still has this power over him.
For now, it's enough that Kaeya understands why it was never spoken aloud.