Hearts are a human story: age-old tales of romance and, sometimes, macabre. If not for Shiro, Keith would all but ignore his own and any others.
A week after Shiro comes to Keith’s class and speaks with him afterwards, a much larger kid at the group home knocks into Keith so hard that Keith is winded and his heart is knocked out of his fearful chest, disappearing off a cliff. Keith lies there, gasping in the dirt for breath and ribcage ringing hollowly. He thinks he might die like this, thinks about his father’s heart had always been gone--whoever his mother had been, she had not or would not reciprocate with the gift of her own heart--and how he had lived each draining day of life without a heart until he’d died.
This is what is rarely said of hearts: you can live without your heart, more easily when you live with another’s. But only soulmates--so, so rare, marked in history by treasured anecdote--can carry each other’s heart indefinitely. The weaker the bond between the pair, the more brief their trade.
Shiro is suddenly there without Keith knowing how--rare, he is always on his guard these days--and gently turning him onto his back. His mouth moves but Keith can’t hear him over his gasping breaths. Shiro frowns and tucks his fingers into his chest; his heart is a glistening violet-blue that sinks easily into Keith’s chest. Blood roars in his ears with the strength of the borrowed heart before receding gently to the background.
“Keith, are you okay?” Shiro asks, patient as if it’s the first time he’s asking. His fingers curl gently around Keith’s wrist at his pulsepoint, other hand supporting his elbow.
Keith nods mutely. “I need--” he says finally, struggling to his feet, looking out over the cliff and seeking his heart. “I need--”
It’s muddy terrain; Keith slips and Shiro catches him easily. Even without his heart, Shiro is dizzyingly steady. “How can I help?” he asks.
Keith’s hands are trembling still. He can’t stop them. Fear wars within him before he finally speaks; Shiro didn’t need to lend him his heart. Keith probably wouldn’t have died without it, only felt like it. “My heart,” he admits. “It went down the cliff.”
Shiro’s eyes go sharp at this, scanning first Keith’s body and then the open yard. Then he’s shedding his motorcycle jacket, zipping Keith into it without a care for the mud that will transfer from one to the other. Keith hadn’t realized how chilled he’d been feeling until then, even on an overall pleasant day.
“Stay here,” Shiro says, turning his gaze to the cliffside.
“But your heart--” Keith says.
Shiro shakes his head and beams down at Keith. “Hold onto that for now,” he says, then begins down the slope.
Sat on the ground, waiting and recovering, Keith wonders how Shiro will carry his heart back to him, if he will shy away from touching it directly or if he will carry it where his own heart normally nestles. Instead, Shiro keeps Keith’s heart cradled like a fragile, living thing in his palm, like it’s made of pomegranate seeds instead of resistant garnet. He scales the steep slope singled-handed to kneel before Keith and offer him his heart back.
The strangeness of Keith’s body has eased by then and he dips fingers into his chest to return Shiro’s heart. A part of him mourns when they carefully exchange hearts--mourns what must be an imagined security from carrying Shiro’s heart. Keith has never carried anyone’s heart before; his father’s hadn’t had his own for years, and it was too intimate for anyone else.
Shiro’s heart is iolite, he says, what they call water sapphire. It’s a stone of exploration and of illumination. Fitting for a pilot of any sort. Fitting for a future cosmonaut. Keith’s heart is a many-faceted garnet, of fire and chaos and purification.
“Your heart is beautiful,” Shiro says, smiling kindly down at him.
“Thank you,” Keith says for too many things.
He’s accepted at the Garrison before he meets the minimum age requirement. He challenges anyone to defy the support of someone half of what Shiro is.
A week before the Kerberos launch, they sneak onto the roof to watch the stars and share too-hot tea.
“Is there anything you want,” Keith asks over the nerves.
“For you to be waiting for me when I get back,” Shiro says immediately, tucking Keith under his shoulder.
Keith ducks his head and laughs. “Besides that. Before you go.”
Humming, Shiro shrugs.
“There must be something.”
“It would be too much to ask,” Shiro admits, avoiding eye contact. Keith frowns.
“There’s not much you could ask that I wouldn’t do,” Keith says, because it’s true. “Tell me what you would ask.
Shoulders hitched up to his ears, Shiro looks young. “I’d ask--if I could carry your heart, if only for a little while.”
Keith’s fingers slip almost automatically into his chest and wrap around the pulsing warmth of his heart.
“Here,” Keith says before Shiro can get loose from him and depart the roof at a sprint, slipping his heart into Shiro’s hands.
“But your--” Shiro says, cupping Keith’s heart tenderly against his chest while his other hand dives for his own heart. Remembering, doubtless, the only time he’d seen Keith without his heart.
“You can give it back to me when it gets uncomfortable,” Keith says, heart unpanicked in exactly the opposite way to years before, knocked cruelly into the open.
“Carry mine until then, at least,” Shiro says, eyes worried. Keith accepts simply to settle him.
Throughout the week Keith catches Shiro brush his fingertips across his chest in wonder, like it’s the most precious gift he’s ever been given.
“You should hold onto it until you come back,” Keith says, seeing Shiro try to steel himself to return the borrowed heart.
This time, Shiro looks at Keith like he’s something to wonder at. Responsible thoughts trip over his tongue--at carrying another’s heart into space, at the possibility of slowly rejecting it and compromising the mission.
“I trust you,” Keith says, because he does and Shiro needs to hear those words. “Take it out if you need to, but never for anyone else but yourself.”
“You’re amazing,” Shiro says, eyes shining. When they hug, they feel each other’s heart beat steadily.
In the Galra’s gladiator cells, Shiro closes his eyes as regret for carrying Keith’s heart into danger overpowers the guilty relief that he has something of Keith with him. When he opens his eyes again there is only the determination to survive, to safely return Keith’s heart to him.
What’s this, the druids hiss as they stand around the table. Keith’s heart glows with impassioned heat. Shiro can only feel it, not see it as the druids apparently can. Call the High Priestess.
“How can it be pilot error?” Keith demands. “Where are the flight records?”
“You forget yourself, Cadet,” Iverson says evenly. “Any pilot can fall into pilot error. I suggest that you accept that Pilot Shirogane is dead, lest you follow his footsteps there, too.”
“He’s not dead,” Keith says numbly, hand creeping to his chest. He’d know if Shiro died--his borrowed heart would weaken, if not outright die. Shiro’s heart is strong and gentle in his chest.
Iverson’s face darkens and he begins to yell words that Keith can’t track. But his hands reach out like they might tear Shiro’s heart out and squeeze. Instinctively, Keith lashes out with his fist, Shiro’s guidance echoing in the motion.
He leaves while Iverson’s still sprawled out unconscious across his desk.
Something sings through the sky from far away. So, too, sing the heart in Keith’s chest and the mystery in the desert. Keith gears up and follows the stardust trail through the night sky back to earth.
Until his hand brushes Shiro’s cheek and the heart comes alive, Keith has only hope and Shiro’s heart.
Shiro says nothing and Keith clings to the borrowed heart.
Ulaz sees their human hearts and Keith sees familiarity in his balade. But then Ulaz is dying with whatever answers he carried and the only way to the truth is through the Blades of Marmora.
Wandering through the Castle, Kolivan catches Keith shirtless as Shiro treats his injuries. The heart leaks a fragile violet light that leaks weakly through his ribcage even as it struggles to sing something tender and reassuring.
“Yours is not the first heart I’ve seen like that,” Kolivan says.
“I thought we were the first humans you’d met,” Shiro says while Keith sways under his hands and the heat in Shiro’s chest pulses higher as if to self-soothe.
“You are,” Kolivan says, and nothing more.
Shiro is gone but not. The others have given up, it seems, only Keith and his borrowed heart sing grief and devotion. It’s a lot like the aftermath of Kerberos, in a way.
With Keith in the pilot’s seat, the Black Lion comes alive and Shiro’s heart shines through Paladin Armor for the first time. Keith wants to weep.
Then Shiro comes back and something is wrong. Like he’s changed in countless tiny ways, like he carries only the imprint of Keith’s heart within him.
Keith tries to assemble a tree out of logic. The only viable root cause is in Keith supplanting Shiro in the Black Lion, however unwillingly. Keith can fix this.
What hurts most is when the heart grieves and Shiro doesn’t. Keith throws himself into being a Blade to cope.
Krolia is a revelation of sorts. Only as they flee the base does he do the impossible and recognize his father’s heart in her chest, only as she loosens her armor and unleashes a glow like a sky brushed by wildfire.
Now he knows how Kolivan has seen a human heart far beyond the reach of human exploration.
In the astral plane--inside Black--Shiro’s chest shines a bright, living red.
“I died, Keith,” he says, but there’s Keith’s heart burning for him and Shiro’s heart still pumps for Keith.
Then Keith is waking up in the Black Lion again with the clone collapsed behind him. He’s barely breathing. Keith closes his eyes and slips Shiro’s heart from his chest, like it might anchor the way it had for Keith so long ago.
Look through the Black Lion’s eyes, Shiro says, voice still strong in Keith’s ear without the mainstay of a heart. It’s different but Keith could fight like this.
The weight of doing so much catches at Keith with dragging hands but Shiro isn’t gone. As much as Shiro had asked that he never give up on himself, Keith knows he will never give up on Shiro as well. Under Keith’s hand, Shiro’s heart burns and glows violet, lingering long past the the lightshow of Allura’s Altean Alchemy.
“You saved me,” Shiro sighs as he slumps into Keith’s hold, sighing again that his chest is too full. His fingers shift against the chestplate and draw his shining heart out. The others gasp--at least the humans do--before a rare tactical courtesy prevails and they all about-face in the name of the concept of privacy. Keith catches Shiro’s shaking hand and guides it, and then the heart is sinking into his chest like a promise of eternity. It is a human promise born of a human heart but it sings of the cosmos.