Chapter Text
Jin is halfway through a rice cracker when the future behaves normally.
Shun waves too cheerfully, crumbs still clinging to his fingers, and Jin laughs, waving him off with the hand not holding the snack.
“Don’t run in the hallway,” he calls, already crunching down on the last bite.
The kid turns, grinning, and disappears around the corner.
Jin chews, half-lidded eyes lazy.
The corridor smells faintly of vending machine juice. Border HQ, alive and mundane and exactly as it should be.
As people disperse, there’s less flicker at the edge of his vision. Branching threads closing. Soft overlap of possibilities that usually hums in the background like white noise descreases.
“…Another peaceful day.”
That’s when he feels it.
Presence.
Close. Too close. Behind him.
Jin starts to turn—
And suddenly there is weight.
A body slams into his back, arms wrapping around him hard, pulling him off balance. The impact knocks the breath from his lungs, the remaining crumbs of rice cracker scattering from his hand as he stumbles forward—
Only he doesn’t fall.
Because the arms around him tighten.
And tighten.
Not crushing.
Anchoring.
Like the man holding him is afraid the ground itself might give way.
“—Whoa, hey—!”
Jin’s hands come up instinctively, palms pressing against a solid chest. The heartbeat beneath them is fast. Wild. Too loud.
The grip doesn’t loosen.
It grows heavier.
Jin feels the weight of the man’s forehead press briefly against the back of his shoulder, like he’s bracing himself. Like he’s confirming something real.
The Side Effect goes dead silent.
No futures.
No warnings.
No anything.
Jin’s smile is gone now.
He twists his head just enough to glimpse the man’s face over his shoulder—
Startled.
Eyes wide, pupils blown, like he hadn’t believed this would work. Like he hadn’t believed Jin would still be here.
Then pain, sharp and immediate, cracking straight through his expression.
And then—
Relief.
So intense it almost buckles him.
The man exhales, a sound that’s half a laugh and half a sob, breath shuddering against Jin’s neck. His arms tighten again, fingers curling into Jin’s uniform like he’s afraid to let go even for a second.
And Jin realizes something terrifyingly specific.
This man is happy.
Devastatingly happy.
Like someone who has been starving and just found food.
“…Okay,” Jin says carefully, voice low, trying not to startle him. “Buddy. I dunno who you think I am, but—”
“Hey.”
The word slices clean through the moment.
Sharp. Irritated. Familiar.
Jin feels the man stiffen behind him.
Footsteps approach, measured and heavy, and the air shifts with a presence Jin knows as well as his own heartbeat.
“Get away from him,” the voice says flatly. “Now.”
The arms around Jin hesitate.
Slowly, reluctantly, they loosen just enough for the man to lift his head.
Jin turns with him.
And freezes.
Because standing a few meters away is a man with the exact same face.
Same height. Same build. Same beard patterns. Same expression that says violence is optional but encouraged.
Tachikawa Kei stares at the stranger.
Then at Jin.
Then back at the stranger.
“…What the hell,” he mutters. “Why do you look like me?”
The man doesn’t answer.
He looks at Tachikawa only briefly—like checking a detail he already knows—before his gaze drops back to Jin.
Up close, Jin sees it all now. The exhaustion carved deep into his features. The grief worn so thin it’s practically translucent. This isn’t confusion.
This is recognition.
The man swallows.
His voice, when he speaks, is quiet. Steady. Right on the edge of breaking.
“You’re not my Yuuichi.”
Jin doesn’t see a past.
He doesn’t see a future.
But something settles in his chest with awful clarity.
This man has already lost him.
And for one impossible moment—
He got him back.
Behind them, alarms begin to wail.
⏱︎ ⏱︎ ⏱︎
They don’t put him in a cell.
Border never does, not when the anomaly is cooperative.
Instead, it’s a sealed briefing room two levels underground—white walls, trion-dampening panels humming quietly, a long table that has seen too many disasters explained over cold coffee.
Jin sits across from the man with Tachikawa’s face.
The real Tachikawa stands to Jin’s left, arms crossed, jaw locked. Shinoda and Kinuta watch from the far end, silent.
The man sits straight-backed, hands folded loosely on the table.
He hasn’t looked at Jin since the hug.
That hurts more than Jin expected.
Jin breaks the silence first.
“So,” he says lightly, like they’re discussing tomorrow’s weather. “You wanna start with the obvious part, or the part where my Side Effect refuses to acknowledge your existence?”
The man exhales through his nose.
“Branching,” he says. “Let’s start there.”
Jin’s fingers still.
Real Tachikawa’s eyes sharpen.
The man lifts his gaze—not to Jin, but to the wall behind him, like he’s organizing something painful.
“People like to call it time travel. It’s not. Time only moves forward.” He taps the table once. “What branches is outcome.”
He glances at Jin now.
“Every decision creates divergence. Most of them collapse back into the same result. Some don’t.”
Jin hums softly. “Parallel universes.”
“Yeah.” The man’s mouth twitches. Not a smile. “Only you never liked that term.”
Jin freezes.
“…Did I?”
The man closes his eyes.
“Yeah.”
Real Tachikawa straightens. “You’re saying you came from the future.”
The man shakes his head immediately. “No.”
Then, more carefully:
“I came from a universe where 'it' already happened.”
Silence stretches.
Jin leans back in his chair, gaze thoughtful, but there’s something tight behind his eyes now.
“Okay,” he says. “So what makes my universe special?”
The man’s jaw flexes.
“Nothing.”
That lands worse than if he’d said everything.
“You were the same everywhere,” he continues quietly. “Same Side Effect. Same bad habit of watching outcomes no one asked you to watch.”
Jin doesn’t interrupt.
“You saw burials,” the man says. “Over and over. Futures where we won, futures where we lost. Futures like Kakizaki's where people lived long enough to die old.”
His hands curl slightly.
“And you watched every version of yourself attend them.”
Jin’s voice is very calm. “I don’t see the past.”
“I know,” the man says immediately. “You saw forward. You just stayed long enough for it to feel like memory.”
Real Tachikawa looks sharply at Jin now.
The man continues, voice roughening.
“You were the only one who did that to yourself. Everyone else looked away. You didn’t.”
Jin swallows.
“…That still doesn’t explain why you’re here.”
The man finally looks directly at him.
“In one branch,” he says, “you decided the only way to guarantee survival was to remove uncertainty.”
Jin’s stomach drops.
“…A Black Trigger,” Jin murmurs.
Shinoda shifts.
Real Tachikawa’s hand tightens into a fist.
The man nods once.
“Your own.”
The room goes cold.
Jin lets out a breathless laugh. “Nope. Don’t love that idea.”
“You didn’t either,” the man says. “That was the problem.”
Jin’s smile fades.
“You hesitated,” the man continues. “Because you knew what it would cost. You knew it would lock the future.”
Jin’s gaze drifts to the table.
“…Yuuma?” he says quietly.
The man nods again.
“He stopped you,” he says. “Not because he understood everything. Because he was trying to keep four-eyes alive.”
Real Tachikawa’s head snaps up.
“And that,” the man says, voice breaking just slightly, “is where everything went wrong.”
No one speaks.
Jin finally looks up.
“Define ‘wrong.’”
The man inhales slowly.
“In stopping you, the branch destabilized. Decisions stacked on decisions that were never meant to coexist. Futures stopped collapsing cleanly.” He gestures vaguely. “That’s where the black hole theory comes in.”
Jin tilts his head. “Okay, now you’re losing me.”
“Good,” the man says quietly. “Means you’re still ahead.”
He leans forward, forearms on the table.
“When too many unresolved futures pile up, causality folds in on itself. Not destruction—compression.” His eyes flicker to Jin. “A universe trying to correct itself.”
Jin’s Side Effect hums faintly, uselessly.
“And your universe?” Jin asks.
The man’s voice is almost flat.
“It corrected.”
The words don’t echo.
They don’t need to.
Jin doesn’t ask the forbidden question.
Instead, he asks:
“…So why me?”
The man studies him for a long moment.
“Because your future here hasn’t collapsed yet,” he says. “And because I can’t save mine.”
Real Tachikawa finally speaks.
“Then why show up at all?”
The man looks at him.
Because you still talk like there’s time left.
He doesn’t say it.
He just answers:
“So you don’t repeat us.”
Silence.
Jin closes his eyes.
Not in fear.
In calculation.
“…Yeah,” he says softly. “That checks out.”
And for the first time since the hug—
The man looks terrified.