Chapter Text
The ruins smelled of old rain and older stone.
Diluc pressed his back against a crumbled pillar, claymore humming faintly with Pyro energy at his side, and listened. Water dripped somewhere in the darkness ahead. A ruin hunter's gears clicked and whirred in the distance - inactive, probably, but worth keeping track of. The intel had mentioned Fatui operating in these ruins north of the city, some kind of supply cache or smuggling route, and he'd been more than happy to handle it himself rather than delegate to the Knights.
Especially today.
He exhaled slowly through his nose.
Especially today.
The spring solstice celebration from last night still clung to him like woodsmoke in fabric. He could still hear the din of Angel's Share at capacity: laughter and fiddle music and Charles calling for another round of dandelion wine. Could still feel the warmth of too many bodies packed into a tavern decorated with paper lanterns and fresh-cut lavender. Could still see the way the candlelight had caught in Kaeya's eye as he leaned against the bar, nursing the same goddamn drink for two hours.
Waiting.
Waiting for what, exactly? For Diluc to magically forget everything that had passed between them? For him to just... what, pull up a stool and start chatting like old times? Like he and Kaeya hadn't-
Diluc's jaw tightened. He pushed off the pillar and continued through the ruin corridor, boots splashing through shallow puddles. The walls here were marked with old Mondstadt script, barely legible, something about Barbatos and the old aristocracy. Normally he'd pause. Read. History mattered, even when it was carved in places most people would never see.
He didn't pause.
The argument played on repeat in his skull, an accompaniment to the drip and echo of the ruins. Kaeya's voice, low and carefully casual: "The spring solstice was always your father's favorite too, wasn't it? I remember he used to let us have a glass of wine - just one - when we were young..."
And Diluc's response, sharper than he'd intended even at the time: "Don't."
Just that one word. But it had been enough.
Kaeya's expression had flickered - there and gone in an instant, that careful mask almost slipping. Almost. He'd smiled instead, that easy, infuriating smile that never quite reached his eye. "My mistake. Forget I said anything."
But he hadn't left. That was the problem. He never just left. He'd stayed at the bar, sipping his drink, watching Diluc work the room with that unreadable gaze. And every time Diluc had turned around, there Kaeya was - not looking at him, exactly, but present. A constant pressure at the edge of Diluc's awareness.
Until finally Diluc had snapped.
"If you're here to keep an eye on me for the Knights, at least have the decency to be subtle about it."
The words had landed harder than he'd expected. He'd seen it in the way Kaeya's fingers tightened around his glass, the brief tension in his shoulders before he'd relaxed into that practiced slouch.
"Not everything is about the Knights, Diluc."
"No? Then what's this about? Because you've been hovering for weeks, and I'm tired of pretending I don't notice."
Silence. The fiddle music had seemed louder in the space between them.
"Maybe I just wanted to spend the solstice with...family."
The word had felt like a slap. Family. As if Kaeya had any right to use that word. As if he hadn't proven exactly how little it meant to him when he'd-
"You lost the right to call us that a long time ago."
Diluc hadn't stayed to see Kaeya's reaction. He'd turned on his heel and walked out of his own tavern into the cool spring night, leaving the celebration and the noise and those words behind him.
Except he hadn't left them behind at all. Here he was, hours later, stalking through ancient ruins in the dark, and he could still hear that word ringing in his ears.
Family.
A ruin guard clicked to life somewhere ahead of him. Diluc drew his claymore and let the Pyro surge through him, hot and bright and familiar. The construct turned its single eye toward him, gears grinding, and he was moving before it could fully activate - one swift vertical slash that bisected the eye, a second horizontal strike that severed the neck. It crumpled with a groan of tortured metal.
He didn't even break stride.
Maybe, on another night, he would have softened, just slightly. The word wouldn't have rankled under his skin like it had. He might have sighed and looked away and maybe said nothing, and just poured another glass of Death After Noon, and they could have sat there in some silence that was vaguely comfortable and pointedly not painful, and he wouldn't have felt like a total ass.
The Fatui cache was supposed to be deeper in the ruins, through a series of chambers that had once been a noble family's tomb. Diluc navigated by memory and instinct, the map he'd studied earlier merging with the physical space around him. Here, the corridors widened into a receiving hall. There, a collapsed staircase led to the lower levels. He took an alternate route, climbing down a half-crumbled wall into the darkness below.
His Vision cast flickering shadows across the walls - gods and heroes depicted in faded paint, their faces worn to ghostly suggestions by centuries of neglect. In better circumstances, he might have felt something. Reverence, maybe. Or at least curiosity.
Right now, he just felt irritated.
The worst part - the part he refused to examine too closely - was that he knew he'd been cruel. He knew it. He'd seen it in Kaeya's face, that brief instant before the mask had slipped back into place. The flash of something raw and hurt that Kaeya would never, ever admit to feeling.
Good. Let him hurt.
Diluc's grip tightened on his claymore. The thought should have brought satisfaction. It didn't. It just sat in his chest like a stone, heavy and uncomfortable and utterly refuseable.
Kaeya had no right to hurt. He was the one who'd lied. He was the one who'd kept his secrets wrapped in shadows and smiles until the truth had torn through their lives like a wildfire. He was the one who'd chosen his path - chosen the Knights, chosen his schemes, chosen everything over the family that had taken him in and loved him and trusted him.
And now he wanted to show up at the spring solstice and reminisce about their father? Wanted to use that word like it meant something? Wanted to stand there with that wounded look in his eye and make Diluc feel like the villain?
No.
The tomb chambers opened up ahead, just as the intel had suggested. Diluc could see the glow of a makeshift Fatui camp - lanterns and a portable stove, supply crates stacked against the far wall. Two agents sat by the fire, speaking in quiet Snezhnayan. A third stood watch near the entrance to an inner chamber.
Diluc counted them silently. Assessed. Decided.
He moved.
The first agent died before he could shout - a burst of flame and a claymore strike that left nothing but ash and the smell of charred flesh. The second managed to cry out, reaching for their weapon, but Diluc was already there, Pyro singing through the air. The watch guard lunged at him from behind, a Cryo blade forming in their hand, and Diluc spun to meet them.
Cryo against Pyro. The clash hissed and sparked.
He thought of Kaeya.
He always thought of Kaeya when Cryo filled the air. Couldn't help it. The element was too intertwined with memories - sparring in the courtyard, Kaeya's laugh, the way frost had crackled across his brother's shoulders when they clashed -
Not his brother.
Diluc ended the fight with a savage overhead strike that drove his claymore through the agent's guard and into their shoulder. They dropped, screaming, and he finished it with a burst of flame that silenced them.
The cache was secure. He should check the crates, document the contents, report it to Jean-
No. Not the Knights. He'd handle this himself, like he always did.
Diluc moved through the camp methodically, checking bodies and crates alike. Weapons. Supplies. Correspondence that might be useful. He tucked a few letters into his coat and turned toward the inner chamber the watch guard had been protecting.
The ley line was there.
He recognized it immediately - that shimmer in the air, that sense of something vast and ancient pressing against the fabric of reality. Ley lines weren't uncommon in ruins like these; they were the veins of the world, carrying memories and elemental energy through Teyvat's bones. Usually they were dormant. Usually they were stable.
This one, though, was neither.
Diluc stopped at the threshold, frowning. The ley line pulsed with an unsettling rhythm, its usual blue-green glow shot through with veins of something darker. Volatile. Wrong. He could feel it in his teeth, in his bones, a pressure building behind his eyes.
He should leave. Come back with a team, with scholars who understood ley line instability, with proper containment equipment.
But leaving meant returning to the city. To the tavern. To the celebration still spilling through Mondstadt's streets. To Kaeya, who would still be there, still nursing that drink, still waiting with that patient, infuriating-
The ley line pulsed again. Harder.
Diluc took a step back. Then another.
Too late.
The explosion was soundless and absolute - a rush of light and pressure that picked him up like a doll and threw him across the chamber. He hit the far wall hard enough to see stars, claymore clattering from his grip, and then the light was everywhere, filling his vision, filling his skull, filling everything until there was nothing left but white and the distant sensation of falling.
His last conscious thought, absurdly, was of Kaeya.
Maybe I just wanted to spend the solstice with family.
Then darkness.
He woke to birdsong and sunlight streaming through an unfamiliar window.
Diluc lay still for a long moment, staring at the wooden ceiling above him, trying to reconcile his surroundings with his last memories. This was not the ruin. This was not his room at the Dawn Winery. This was-
His childhood bedroom.
He sat up sharply, ignoring the ache in his head, and stared. The walls were covered in old tournament posters and maps he'd half-forgotten. His first sword hung above the desk, alongside a wooden shield he'd made as a child. The sheets beneath him were worn cotton, not silk, and the window was open to a view of the estate's eastern garden - the garden the way it had looked years ago, before storm damage, before the renovations, and before it was, finally, sold off.
"What..."
His voice cracked. Higher than it should have been.
Diluc looked down at his hands.
Young hands. Smooth and unscarred, without the calluses of years of combat. His arms were thinner, his shoulders narrower, and when he raised a hand to his face, he felt the softness of youth - no stubble, no lines, no evidence that he'd ever seen anything more trying than a fencing lesson.
A mirror. He needed a mirror.
He stumbled from the bed and caught sight of himself in the dressing mirror by the wardrobe. Seventeen. Seventeen. Red hair shorter than he'd worn it in years, face rounder with baby fat he'd long since lost, eyes that still held something like hope in their depths.
"No," he whispered. "No, this isn't- this can't be-"
Footsteps in the hallway. Quick, light, familiar.
A knock at the door.
"Diluc? Are you awake?"
His heart stopped.
He knew that voice. Knew it as well as his own, maybe better - had heard it in memories and nightmares, in dreams he'd never admit to having, in the echo of a hundred arguments and a thousand moments he'd spent years trying to forget.
The door opened before he could respond.
Kaeya stood in the doorway, sixteen years old and achingly familiar. His hair was longer than Diluc had seen it in years, pulled back in a loose ponytail, and his expression was open in a way that the adult Kaeya's never was - hopeful and earnest and completely unguarded. He wore a simple linen shirt and trousers, informal and comfortable, like he belonged here.
Like he was home.
"Good, you're up!" Kaeya smiled, and it was a smile Diluc hadn't seen in so long he'd almost forgotten it existed; bright and genuine and completely devoid of the careful masks the older Kaeya wore like armor. "Father says breakfast is almost ready. He wants to discuss the tournament preparations after, something about your stance needing adjustment?"
Father. The word hit Diluc like a physical blow, and suddenly he couldn't breathe.
Father. Crepus. Alive.
"Are you alright?" Kaeya's smile faded into concern, and he stepped into the room, moving toward Diluc without hesitation. "You look pale. Did you sleep badly? You were tossing when I walked by last night - I almost came in to check on you, but I didn't want to wake you..."
Diluc's throat closed. He couldn't speak. Couldn't move. Could only stare at this boy - this child - who looked at him with such open affection, such trust, such love, as if the years between them hadn't happened yet. As if nothing had been broken.
As if they were still brothers.
"Diluc?" Kaeya reached out and touched his arm. Gentle. Concerned. "You're shaking. What's wrong?"
Everything.
Diluc stepped back, pulling his arm away, and watched Kaeya's expression shift from concern to confusion to something that looked horribly like hurt.
"I'm fine," he said, and his voice sounded wrong in his own ears. Too harsh. Too old. "Just... tired. I'll be down shortly."
Kaeya didn't move. His eye - that single, beautiful eye that Diluc had spent years trying not to think about - searched Diluc's face with an intensity that seemed too perceptive for sixteen.
"Are you sure? Because if something's wrong, you can tell me. You know you can tell me."
Can I? Diluc wanted to scream. Can I really? Or will you just lie to me again? Keep your secrets and your schemes and your twisted loyalties until the moment comes to use them against me?
But this Kaeya hadn't done any of that yet. This Kaeya was still innocent - still the boy who followed Diluc everywhere, who believed in him completely, who had never yet revealed the truth of where he came from.
This Kaeya still had the capacity to hurt him in ways the older Kaeya never could again.
"I'm sure." Diluc turned away, toward the window, and forced himself to breathe. "Go on. I'll be there in a moment."
He could feel Kaeya's hesitation like a physical presence. Could feel the weight of that gaze on his back, the questions that Kaeya wasn't asking, the concern.
"...Alright."
The word was quiet. Uncertain. Diluc listened to the sound of Kaeya's footsteps retreating, the soft click of the door closing, and only then did he let himself sag against the windowsill.
Below, in the garden, Crepus Ragnvindr was directing a servant in the placement of new flower boxes. His father's voice drifted up through the open window, warm and commanding and alive, and Diluc felt something crack open in his chest.
Alive. His father was alive. Young and strong and alive, and somewhere downstairs, Kaeya was setting the table for breakfast, and outside, the sun was shining on a world that hadn't yet been shattered by truth and death and betrayal.
Five years. He'd gone back five years.
Diluc pressed his forehead against the cool glass and tried to think, but his mind kept circling back to the same impossible thoughts. His father was alive. Kaeya was young. And somewhere in the future - or was it the present? - a ley line was pulsing with volatile energy, and he was lying unconscious on a ruin floor, and none of this could possibly be real.
Except he could feel the glass beneath his palms. Could hear the birds and his father's voice and the distant clatter of dishes. Could smell the flowers from the garden and the lingering scent of last night's rain.
This was real. Somehow, impossibly, this was real.
And Kaeya - young Kaeya, innocent Kaeya - was waiting for him downstairs with that open, trusting expression, having no idea what lay ahead. No idea that in just a few years, everything he believed about himself and his family would be torn apart. No idea that the brother he looked up to would become the man who couldn't stand the sight of him.
Diluc straightened.
He wouldn't let it happen. That was the answer, wasn't it? He'd been sent back - by the ley line, by fate, by some cosmic joke he didn't understand - and now he had the chance to change things. To prevent the mistakes that had led to their family's destruction. To protect his father from the death that awaited him.
To keep Kaeya from ever getting close enough to cause damage.
It was simple, really. In this timeline, Kaeya was just a boy. A boy with secrets, yes, but secrets that hadn't yet been revealed. A boy who followed Diluc everywhere, who hung on his every word, who believed in him with the wholehearted devotion of someone who had never been betrayed.
All Diluc had to do was distance himself. Let Kaeya down easy, before the attachment could deepen into something dangerous. Keep him at arm's length until whatever cosmic force had sent him here decided to send him back.
It was the logical choice. The smart choice. The only choice that made sense.
So why did the thought of that open, trusting smile faltering make something in his chest twist painfully?
Downstairs, Kaeya laughed at something, one of those bright, unguarded laughs that the older Kaeya had trained himself out of years ago. The sound drifted up through the floorboards like a memory, sweet and sharp and utterly devastating.
Diluc closed his eyes.
This is for the best.
He didn't believe it. Not even a little.
But he would anyway.