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51% of Your Heart

Summary:

An exploration on an alternate universe where Katsuya and Shizuka are already at the orphanage when Seto and Mokuba arrive after their parents' death. Friendship blooms between the two opposite boys as hardship brings them together. But when Seto's plan to be adopted by Gozaburo comes to fruition and they're separated, how will they be able to find one another again?

Notes:

I have always loved Seto and Mokuba's past as it is explored in Noah's virtual arc. Their time in the orphanage, how that shaped them. I wanted entire episodes of that dynamic, and more of Seto after they were adopted, how he was abused and how that would inevitably change him into the ruthless eldest Kaiba we all know and adore.

But then I decided, why not make it sadder? Let's make Katsuya and Seto friends first, then rip them apart and figure out how Seto navigates that.

So... here's this, or the start of this, anyway. I'm just going to yeet what I have and hope it sticks to something. Enjoy!

Thank you as always to Alecto for cheering me on despite how long this has been in my documents folder. <3

Chapter Text

“Checkmate.”

“Arrrgh, again?!”

The clatter of old wood pieces plinked onto the linoleum followed by a frustrated growl.

Seto crossed his arms over his tattered knit sweater and watched the chess pieces skitter with a frown, “You didn’t focus, Katsuya! I told you to look ahead of what’s happening on the board, not just what you see.”

“But tha’ doesn’t even make sense!” Katsuya whined and pulled at his hair, then flopped down to mope face first onto the desk. His head was spinning with all the rules that Seto barraged his tired brain with. What all the queen could do, what all the king couldn’t do. Then there were the tall skinny pieces he couldn’t remember the names of and the foot soldier pawn things that could only kill the enemy if they moved a certain way that he could never remember. His hair fanned over most of the board to fuzz it out like he wanted to fuzz out all the stupid rules.

“You dropped this, Kat,” a tiny voice said way too close. Katsuya grunted, then a mop of raven hair peeked up from the edge of the desk to deposit a black knight with its nose missing back to relative safety, as if being in Katsuya’s orbit was anywhere close to safe. Giggling, Mokuba dropped back below the desk horizon line to collect the rest of the pieces like a little black blur. To Katsuya, the younger brother’s hair was like the mane of a horse bouncing as if running through some open prairie. His mind latched onto the thought just to attempt to escape from this room and this stupid game.

“Thanks, Moki,” Katsuya sighed and turned his head to one side, his fingertip poking at the knight’s nose before Seto snatched it back up and shooed the blond off the board to replace the pieces to their starting positions. Ugh, Seto was such a stickler about making sure the pieces all went in their proper place. How was he supposed to remember all this?

Katsuya peeled himself up off the desk, but his shoulders drooped. “I’ll never get this game, Seto. Why would a castle even be able ta move? It’s supposed ta be a wall. Walls are walls. Dun’ see the walls movin’.”

“They create walls with the way they move on the board,” Seto replied with a huff. “And that’s a knight, not a rook.”

“It’s a horsie,” Katsuya retorted, with indignation. “Even looks like one.”

Seto glared. “It’s a knight.”

Katsuya stuck out his tongue at him. “It’s just a silly game, why you gotta take it so serious anyway?”

Seto sighed in a way that blatantly said it wasn’t the first time he’d had to explain himself in such a fashion. “It’s not just a game, Katsuya. There are tournaments and adults that devote their entire lives trying to find the best strategy. There are competitions, too, big ones with money prizes. But fine, if you’re gonna be a whiny baby about it, move over and let Moki play.”

Baby? He wasn’t a baby! Katsuya’s face turned red and he held his breath and puffed out his cheeks at Seto’s unimpressed stare.

“Uuuuugh,” Katsuya exhaled and threw his head back with a dramatic sigh. Stupid Seto knew all of his tells for when he was actually mad and when he was just blowing hot air out of his ears. Conceding, he oozed off the chair. “Fiiiine, you play your strategy thing. I’m gonna go find Shizuka.”

“Better luck next time, Kat!” Mokuba bounced over to take his place, depositing all the pieces he’d collected. “I’ma get you this time, nii-sama!”

Seto watched Katsuya go with an unreadable expression, then blinked and stretched his face with a grin, which he directed at his brother. “I’d like to see you try, Moki.”

***

“Did you learn anything new playing chess with Seto-kun today, onii-chan?” Shizuka asked, her big green eyes peering down at him from the top bunk.

“Yah, I learned he’s a big bully,” Katsuya grumped, staring up at the stupid broken fan with the three snapped off paddles that the adults never fixed in all the time they’d been there. The middle one looked like a shark fin breaking through the ocean waves, and sometimes when he stared at it too long he’d dream about little sharks eating his ankles off when he’d step in puddles.

Shizuka just giggled. “You don’t mean that.”

“I do!”

“You don’t,” his sister insisted, and Katsuya deflated, rubbing at his eyes.

“...I don’t.”

“Told you.”

“He jus’ makes me feel stupid sometimes,” Katsuya sighed, throwing his arms up over his face and muffling his voice. “He’s so smart, and he has ta say all these things so many times and I still jus’ don’t get it, then he gets mad, an’ I get mad, then I throw stuff, then he gives me this look.”

Katsuya sat up and impersonated Seto by crossing his arms and looking up at Shizuka to give her a huge exaggerated sigh and a glare. Shizuka laughed and laughed, and Katsuya had to hold back from breaking into a giggle fit himself and breaking character.

“Like ‘dat.”

It took Shizuka some time to calm back down, but when she did she popped her head back over the side like a little auburn meerkat. “Maybe chess isn’t for you, onii-chan. But that’s okay! You’re still so good at other stuff! Like making us smile by doing funny things… and building sand castles. And eating all the extra food in the kitchen and getting some for me and Moki-chan and Seto-kun, too. And being the bestest big brother a sister could ask for.”

Katsuya flopped back onto the floor. The uneven click of the fan that did nothing to cool them was the only sound, and then he sighed. “...How’d ya get so smart, sis?”

Shizuka giggled again. “I listened to Seto-kun, silly.”

Katsuya groaned.

***

Over a year and a half. That was how long Katsuya and Shizuka had been in this awful, dreary place.

In the beginning, Katsuya had been hopeful that they wouldn’t be there long, that there’d be some perfect young couple that would just fall in love with Shizuka’s beautiful happy smile and big green eyes and see him laugh and grin and protect his sister so well that they’d get swept right up into their dream family together.

Psh. Yeah… that didn’t happen.

That was just a fantasy for silly children with silly hopes and dreams.

It’d never crossed his mind that the one thing that would hold them back the most would be the other children.

Apparently there was a hierarchy within the ranks of the orphanage that they’d initiated just by being thrown into the fire, to either be chewed up and spat back out again or chewed up, toughened up, and learn to survive to live another day. They were bullied so badly that he’d had to calm Shizuka down every night in their dingy, smelly room, petting her hair and whispering that it’d be alright, that they’d find a new family that would love them and smile and not do those awful things that kept their real mom and dad from being with them and taking care of them, even while he sported new bruises or scrapes to protect her every day.

He’d fought his way through the stupid mouthbreather kids until they learned to keep their distance from both him and his sister. Katsuya kicked and punched and bared his teeth like a little animal with his fists clenched. It’d worked, too, but doing that had ostracized them in the process, making them the lone brother and sister pair. And, it turned out, the ones least likely to be adopted because they were going together or they weren’t going to go at all, and even less likely because of Katsuya’s reputation to throw punches first and ask to be adopted second.

Then Seto and Mokuba arrived.

It was hard to believe sometimes that day was almost a year ago.

Katsuya remembered it like it was yesterday, when he’d peered around the doorway of the play room to the front gates with Shizuka at his hip. There was the flurry of adult commotion that was a clear indicator that either new blood was about to be chucked into the mix, or someone had arrived to take a look at their meager offerings of children to be gawked at. It’d turned out to be the former, which never failed to create the rippling whisper effect among the other kids with alarming speed.

Mokuba had looked so scared, his little fingers clutching so desperately to Seto’s sweater vest while Seto clearly wore the brave face of the two of them. His back had been stiff and he held their few belongings in one little tote bag, glaring at the world and daring anyone to catch his gaze to feel his wrath.

Katsuya had, and Seto had glowered at him and took a half step over to shield his brother, and Katsuya had frowned and looked away. It was almost the spitting image of when Shizuka and Katsuya had been thrown into the fray. Clearly Shizuka had thought the same, as she’d been the only one who sat down beside Mokuba on the swing that evening, daring to talk to the new young blood when the elder brother wasn’t immediately nearby.

Mokuba had warmed to Shizuka immediately, and just as Katsuya had walked up to introduce himself to the raven-haired boy, the big brother showed up and had been all but ready for a fight.

But Mokuba’s tittering, genuine laughter at something Shizuka said loosened Seto’s fist at his side and that was all the opening Katsuya needed to offer a hand for the chance at kinship. Seto had looked down at his hand warily, but Mokuba had sealed it when he looked at his big brother with those big amethyst gray puppy dog eyes of his and Seto had sighed, then shook Katsuya’s hand.

Now he and Seto were nigh inseparable, but monumentally different in almost every way one could imagine two children could be. But Katsuya liked that about Seto. He liked that he was quiet and tactical where Katsuya was reactionary and hot-headed. He liked a lot of things about Seto, actually, except when he thought he knew he was right about something, or when he was trying to teach Katsuya how to play chess for the billionth time.

But now that they were friends, Katsuya couldn’t imagine Seto not being right there.

Just like he couldn’t imagine Shizuka being without Mokuba, and tonight he found them playing in their favorite gathering place: the sandbox.

Katsuya walked up with his hands stuffed in his pockets - rebuffed from Seto, who was busy watching the last chess thing on the television to pay him any mind - and settled on the edge of the sandbox to just watch his dear little sister playing with her best friend.

“And here’s the tram station that will take all the kids around the entire park to see all the cool statues and places to play,” Mokuba said, using little matchbox cars for the train, pushing them through the sand and getting the granules locked up in the little rubber wheels. Shizuka placed little plastic army and marine toys along the ‘sidewalks’ to clearly be the kids in the park.

“But the train has to look like something cool and fun for the kids to want to get on it,” Shizuka said, voice serious as she concentrated on the perfect placement of all the toys. “Otherwise it might be scary.”

“Hmm, you’re right,” Mokuba frowned. Then his eyes lit up with a sudden thought. “Hey! Maybe it could be like riding on a dragon!”

Shizuka gasped, then clapped excitedly. “Yeah! Like those ones from that card game you guys play from the tv?”

Mokuba already started piling up sand over the little metal cars to make them look like a little dragon. Sort of. “Yeah, like those! Seto loves that blue one the most. But the black one is pretty cool too.”

“The red eyed one is really cool,” Shizuka said. Katsuya liked that one the most, too. It looked like a big leathery dinosaur, but he imagined if you touched it, you might catch on fire from all the lava in its belly.

“What kinda park is this, Moki?” Katsuya asked, toeing into the sand with his foot as he’d glanced around at all the random mounds and tiny little sticks poked into the sand that didn’t make much sense to him. Mokuba shooed his holey sneaker away all too like his big brother.

“Aww, you’re gonna break the arcade, Kat!”

Katsuya raised his hands up in peace and overly dramatically yanked his feet back and fully out of the sandbox in a way that pulled a giggle out of Shizuka. She gently put back together the little side of the mound that had collapsed.

“It’s the one Seto promised to build me,” Mokuba answered, his hands in his lap now as his voice went soft, “We’re gonna run the whole thing together. He said every kid like us will get to play there for free, and ride all the rides, too!”

Katsuya blinked. Seto hadn’t mentioned anything like that to him, but it sounded like something Seto would do. Katsuya knew how much Seto loathed his situation and what they’d all been through.

“And you and ‘Zuka will have a place there, too!” Mokuba continued.

Shizuka bounced in the sand. “Moki said I could help decorate all the big projects and celebrations he has planned for holidays for the whole park! Wouldn’t that be so cool, onii-chan?”

Katsuya glanced at his sister, saw her big beaming smile at this make believe place Seto was building and all of a sudden, Katsuya couldn’t seem to find his voice. It lodged in his throat and made his eyes water.

She stopped bouncing and her eyes widened as she stared at her brother. “...Onii-chan?”

“I -” Katsuya croaked out, looking between both Mokuba and Shizuka’s growing concern for his sanity as he ran a hand through his shaggy hair.

And then he bolted.

The younger siblings glanced at each other with equal frowns as he disappeared.

***

Despite being constantly surrounded by other kids - and Seto and Mokuba and his sister, of course - the orphanage was often a lonely place. On the particularly lonely nights when the desire for something he’d never had speared right through his chest and left him aching in ways no amount of rest could fix, Katusya found himself up on the highest rooftop of the orphanage with his feet dangling over the edge.

It was the roof for the eldest kids on the premises, the ones that were least likely to be adopted because they were starting to or about to hit puberty and had outgrown their cuteness factor with the adults. He would have been placed there himself, and Seto too, if not for their younger siblings, so he often had to sneak up after curfew to get his fresh air away from everything and everyone else.

He leaned against the bottom rung of the railing and stared out beyond the gates with his chin pillowed on his arms, then sniffed.

That theme park of Seto’s nagged at him, a heaviness yanking down on his stomach and making it feel all knotted and gross.

Because if Seto was going to build them a theme park to play in together… that’d mean he’d have to not be in this stupid orphanage anymore. And if he wasn’t in the orphanage, that meant he’d be adopted out alongside Mokuba, because it was a well-known fact that Seto refused to leave his brother behind just as Katsuya refused to leave without Shizuka.

And that meant that…

Well… Katsuya knew from experience the likelihood of two siblings being adopted out from this place was not particularly high, but two sets of siblings going together in one household?

It was never gonna happen.

So now he was up on the roof, his eyes wet and clumpy as he attempted to escape his own little known reality that the one friend he’d made in this world besides Shizuka was definitely going to be stripped from him someday.

Why? Because Seto was calm and proper where Katsuya was stupid and trigger-happy with his temper, and Seto was the smartest person Katsuya knew. He was so wickedly intelligent that there was no way he’d stay in this place forever.

Some rich family would eventually come to this dump and scoop both Seto and Mokuba up, probably tomorrow because Katsuya had realized it just now, and then the universe would make it so Seto really could build that theme park for kids. Because Seto really was just that smart, he would figure it out. Katsuya fought with his own selfishness, shame curdling in his stomach and turning it sour when the thought that he hoped Seto would never be adopted, or at the very least wouldn’t be adopted first flitted through his stupid selfish brain. What kind of a friend thought those thoughts? Apparently he did.

Katsuya was so lost in the tumble effect of his dark tornado reverie that he almost startled himself right off the roof when the object of his thoughts suddenly settled beside him.

Dammit, now Seto was going to see him crying, and Seto hated when people cried. Katsuya knew from all the times Seto had told Mokuba to pick himself up and be strong, because there was no use in crying. Wiping the snot and tears off his face with his sleeve, Katsuya couldn’t help but try and hide his face in a sad attempt at concealing the evidence.

He sniffed. “Ya shouldn’t be up here. Past curfew.”

A warm shoulder nudged him. “I could say the same about you.”

Katsuya squeezed his eyes shut, still hidden beneath his bangs, and waited for Seto to tell him to quit being a baby. To stop it with the useless tears... But it never came. He didn’t even feel the weight of Seto’s eyes on him, only the easy companionship of hip to shoulder contact.

When he finally got himself under control, he dared a peek and spied Seto with his hands loosely gripping the rail at chest height, staring out into the sunset.

After one more sniff, Katsuya let his own posture relax. He leaned ever so slightly into the contact, and they silently watched the sun drop below the far horizon line of buildings jutting up to swallow it whole.

The sudden sound of Seto speaking startled him. “Would you like to duel?”

Katsuya blinked through his shock and confusion, but Seto turned toward him, his brow slightly pinched like he was unsure. But Katsuya knew his eyes must be deceiving him, because that was ridiculous. Seto was never unsure about anything. “Wha, like that card game that’s been on the television?”

Seto nodded. “Duel monsters.”

Katsuya’s heart sank. Another game that he didn’t know the rules for, and probably couldn’t figure out. From what he’d seen, it looked complicated. But Seto was staring at him, making his palms sweaty with his bright blue eyes and pinched brow that waited for an answer. Katsuya cleared his throat and looked down and wiggled along the roof edge. “Right. I mean. Sure, but I… I dunno the rules. ‘Sides, I don’t have any of those cool powerful dragons like on TV, just those weak ones that Kenichi dropped in that puddle and didn’t want anymore.”

“You make them up,” Seto replied, sounding so matter-of-fact. Like it was the plainest statement in the world.

Katsuya shook his head. “Nu uh. Seen those kids playin’ on the tv. Definitely got rules. Probably as many as chess.”

Seto shifted close enough that his knee bumped Katsuya’s thigh, but neither of them moved away. “No, Kat, I mean… you can make the rules. And we’ll… we’ll play how you want to play.”

Katsuya blinked, but straightened. “Yeah? Ya mean that?”

“Yup.” Seto nodded again. “Here, look, Moki even drew your favorite, you can use it when we play. He said ‘Zuka helped to color it.”

Katsuya had to glance down to take what was offered, once more covering his eyes with his bangs. Which was good, because his throat got all tight on him and he had to fight the swell of affection that threatened to overwhelm him when he saw it.

It was the Red-Eyes Black Dragon card.

Well, it was Mokuba’s incarnation of Red-Eyes. The tournament they’d watched together had drawn animations that made it look like the monsters had come to life in the commercials between duels like a cartoon. When the black dragon with the red eyes had shrieked and flared its wings after popping out of the card, Katsuya had been enraptured, while Seto had only had eyes for that shiny white dragon.

Now he had a Red-Eyes of his own, its mouth full of a fire-engine red crayon colored fireball and eyes to match that was his little sister’s artwork with Mokuba’s sloppy hiragana emblazoning the top to name it.

It was perfect in every way, and Katsuya couldn’t seem to keep his shoulders from trembling as he held back little choked off sobs, his fingertips brushing over the slightly curled edges of the cardstock from where the scissors Mokuba had used didn’t cut it entirely clean.

“Kat?” Seto asked, and his voice even sounded like a frown.

Katsuya shook his head, like that would explain his tears without verbalizing it. How was he supposed to verbalize the crippling fear and certainty that they were going to be separated someday? That this little card might be the last thing that they do together before Seto and Mokuba were carted off to America or somewhere else far away never to be seen or heard from again?

He swallowed and desperately tried to shove it all back. To be a man, instead of a whiny little baby. To be the strong one like Seto; like all the times he was strong for his little sister.

“Okay, l-let’s play,” Katsuya tried to get out, but it sounded all warbled and messy even to his own ears.

“If we play now, you’ll just get the cards wet,” Seto replied, and Katsuya knew sometimes Seto was harsh, but that stung deep. It stung because Seto wasn’t wrong. He never was. Katsuya couldn’t help but curl in on himself and try to turn away, but he felt a warm hand settle on his shoulder. He attempted to pull back out of the hold, but Seto just squeezed to hold him at bay.

“Moki told me you looked upset earlier… “ Seto sighed, and there it was. The disappointment, Katsuya was sure of it. But when Seto continued, his voice was softer and closer, and now there was a warm hand on either shoulder, squeezing gently like the waves that used to lap at his shins on the beach. Katsuya sniffed again to avoid his nose drooling into his lap, but he refused to look up into Seto’s eyes. “You gotta talk to me, Kat. I don’t know what’s wrong. I thought Moki’s drawing would be a good thing.”

Katsuya shook his head again, then croaked out. “It is. I love it.”

Seto hesitated, then asked, “So… why are you crying? Why were you crying when I came up here and found you?”

He wiped angrily at his cheeks to rid himself of the evidence. “It’s stupid, it don’t matter. Let’s just play, ok?”

The hands dropped from his shoulders, and Katsuya wasn’t sure if he wanted to cry at the loss or sing praises for the distance. But Seto wasn’t done.

“We shouldn’t play if you’re upset. We can duel tomorrow.”

A spark of anger flared in Katsuya. He knew he was on the edge of getting a lecture he didn’t want. “I ain’t upset anymore.”

“...Katsuya.”

That spark flared into something more significant at that tone, and his hand curled into a fist, though he did carefully set aside the card so it wouldn’t be damaged. “Dun’ talk ta me like that.”

Now it was Seto’s turn to sound annoyed. Frustrated. “Like what?”

“Like that. Like I’m a little kid like Moki and Shizuka. Like I did somethin’ wrong.”

“Don’t lie to me, and I won’t have to talk to you like that. Tell me what’s wrong, and we can fix it.”

Katsuya held his breath, then gave out a frustrated sigh. The jig was clearly up, and although he hated feeling cornered, Katsuya hated being a liar even more. He wiped his nose on his sleeve before looking up to meet Seto’s expectant gaze.

He opened his mouth to speak, but just like at the sandbox, his voice caught in his throat and refused to budge. Seto continued to stare at him, which only made it worse. A croaking growl ripped out of him, and then all at once the words poured out like a dam had broken free inside him.

“Moki said you were gonna build a gaming theme park for kids like us someday so we could all play together there!”

Quiet fell between them, minus Katsuya’s pants of exertion. Seto only gave him a blank stare in response and waited for him to continue. When he didn’t, Seto prompted. “...And?”

“And…” Katsuya shrugged helplessly, then threw up his hands. “...and that means you’re gonna be adopted, ‘cuz there ain’t no way you can do that in this place. And if you’re adopted with Moki, there ain’t no way all four of us are goin’ together! An’ you’ll leave, and have a happy family that loves ya, and that’s great ‘cuz you should be happy after your parents both died, but… but…”

Seto frowned. Katsuya couldn’t look at him anymore, even as his tightened fists loosened and all that fight drained right out of his shoulders and left him saggy and heavy feeling. He stared down at his lap and sniffed again as shame bubbled into his throat.

“...but I don’t want ya to leave me. Us. An’.. an’ I know that makes me a bad friend. But I just don’t wanna lose you, too. Like… like we lost our moms and dads.”

The silence rang, deafening for long beats. His weakness rang as loud as the silence, and ate at him like those mini sharks that ate his ankles in his dreams.

He startled when Seto’s hand tipped his head up to look at him, the heat of his loose grip making Katsuya’s cheeks redden. He felt like he could get lost in how blue Seto’s eyes were when they gleamed with confidence and assurance. Like how they looked right now.

“Kat… you’re not gonna lose me, or Mokuba.”

“I’m… I’m not?”

Seto shook his head. “Nope. We won’t be adopted together, you’re right about that. But we’re not going to lose each other, either. Because I’m going to make sure of it.”

Katsuya’s brow scrunched. That didn’t line up with anything that Katsuya had rolling around in his mind, a constant whirl of possibilities with none of them going well. But Seto sounded so sure.

“How you gonna do that?”

Seto smiled, “You just have to trust me, Kat. I’ve got it all figured out.”