*screams for centuries* Uwah~ I've finally gotten around to finishing up all the planning for this AU. I'll admit, it took a while to get the plot detailed, but I'm pretty satisfied. I've been reviewing and reviewing and trying to make sure that it's a story that - hopefully - captures the Hamada brothers' relationship while introducing the yandere element to Hiro's personality. I think I managed to pull it off. However, I did not expect this fic to end up being multiple chapters (I'm writing chapter 2 right now XD). I really hope you enjoy the first chappie! My yandere!Hiro fic begins! Please R&R!

I. Secrets

i·dol·a·try

noun

worship of idols.

extreme admiration, love, or reverence for something or someone.

The love between Tadashi and Hiro had always been innocent; a shared intimacy that intertwined them. It weathered the stormy days (agonizing screams of worry clashing with hot yells of defiance) and basked in the golden light of others (gentle reconciliation where they would curl against each other, the ghosts of countless apologies upon their lips).

Strengthened by every single moment.

Every tickle fight. Every real fight. Every late night. Every fun project. Their personal paradise.

When had that paradise been shattered? When had that innocence degenerated into something so sinful? Could this person - who pinned him to his own bed with Microbots (the very embodiment of Tadashi's influence on his baby brother), who kissed and licked and nipped at his lips and neck and ears - be his Hiro?

Why was this the outcome of their relationship?

It wasn't that the thought hadn't flickered across his mind before, joining Tadashi at his Nerd School. As long as it meant being able to work side-by-side with his big brother. That was his goal. It was just that, he had his pride too. He was not going to sit for two to three hours in some boring class to hear some boring professor drone on and on about concepts that he was already familiar with.

He solved complicated equations and algorithms that his parents could not even solve while in elementary school; he built Mochi hover-cat boots; he collaborated on so many awesome projects with Tadashi (like the super cool hover-cart) that inventing had become second-nature. All before he graduated high school at age thirteen.

Not to boast, but he was a pretty successful hustler too. (If the situation ever got out of control, Tadashi would be there at the right moment to save his backside; the perks of having mini GPS trackers sewn into every one of his hoodies.)

Still, even the highs of winning could not compare to the excitement of creating alongside Tadashi. Different perspectives that yielded ideas carefully crafted into something complex, something tangible, something that no universe had the pleasure of witnessing before, something with the Hamada brothers insignia imprinted within its design.

If only he could convince him that Hiro was all he needed. That they could mold the world into their vision once they stuck together. Not because of SFIT and a school of losers who thought they were too brilliant and too special, but because Hiro could teach him everything and more; because Tadashi was the only one worth every second of his time.

When he said he would take him bot fighting that night, Hiro could not be happier. Finally, all his efforts were paying off. Perhaps he could get Tadashi to leave his Nerd School and join him instead. Pull off a heist that none of those underground nobodies could ever dream of.

Of course, Tadashi had other plans.

"What are we doing at your Nerd School?"

"Relax, you big baby. I've just gotta grab something."

Hiro had entertained joining Tadashi at his Nerd School before, but never more seriously than he had today.

Access to advanced technology? Check. Nerds that he had wrongly labeled as snobbish as opposed to being truly intelligent? Check. Closeness to Tadashi at all times because his brother offered to share his personal space and projects with him? Check. Add getting to meet the world-renowned scientist and robotics genius, Robert Callaghan, to the mix and walla! One super amped Hiro is the result.

Incredible ideas aren't born simply from playing Eye of the Tiger in the background, though. Not for Hiro. No, being on Tadashi's shoulders was what got his blood pumping and his mind racing. When they worked as one, perfectly synchronized.

("Pass me the -"

"-wrench."

"On your - "

" - left. Got it."

"Do it this way, it's -"

"- easier.")

Dangling from his brother's shoulders triggered him like clockwork. Why not invent something that personified Tadashi's words? "Look for a new angle." Something groundbreaking. Something with infinite possibilities.

"They're called, Microbots."

"Someone has to help."

"NO!" Hiro had never clung so desperately to Tadashi before. He just felt that if he let Tadashi rush into that blazing hellfire, he would never see him again. Never again feel those strong (if slightly callous) hands pin him to the floorboards when they wrestled; never again hear his soft chuckles whenever Hiro was frustrated with a project; never again see that smile born of blinding light (even when there was a piece of lettuce stuck between his teeth).

A world without Tadashi was one he wanted no part of.

"Hiro! Please! I might be able to save him!"

"No! You can't go in there! You just can't!" In a battle of strength, Hiro could never win, but he would be damned if he didn't give it his best shot. Clawing and screaming, "If you go, I'm going too!" Feral and unrelenting because he could feel the flames licking at his skin, itching to burn it off, to consume both him and his brother; he could taste the thick smoke threatening to suffocate them.

And, in that moment, he knew if he couldn't get Tadashi away from there, they would both die.

Just as he lost his grip, a final plea of desperation upon his lips, they were catapulted backwards. He felt Tadashi curl around him upon impact, checking his vitals, whimpering for his baby brother to open his eyes.

All too soon, the gentle warmth was gone, frozen over by the piercing blares of sirens all around and his brother's heartbreaking wails.

Seeing Tadashi in mourning was as painful as ripping himself in half. Blaming himself for occurrences beyond his limited control. They were inseparable during this time; Hiro clinging to Tadashi like a lifeline, and Tadashi leaving not even their own room without Hiro in tow. There were the rare times when he would quietly request for Hiro not to touch him, but he would never snap when Hiro blatantly disregarded it. Nor when Hiro began sleeping in his bed after he had a particularly violent nightmare about the fire.

("Hiro! Hiro!"

"Tadashi! I'm right here!"

"Please... Oh, please stay with me.")

Tadashi didn't attend the classes he was enrolled in for the new semester. Not until the second week, anyway, after much encouragement (pestering) from Hiro. But it was understandable. The loss of such a revered man had shaken him deeply, had shaken many of them deeply.

So tragic, the accident that dissolved the professor into nothing but ash.

Oh, child, it must hurt to lose such an invaluable invention. No. No, it didn't. Because he had his Tadashi.

Once Tadashi did go back to school, Hiro wished he had kept a tighter hold.

He became akin to a living phantom. Their paths would never cross during daylight. When night fell, Hiro would wait for his return, anxious at first, but eventually assured that no harm would befall his older brother. He would feign sleep in his own bed, waiting until he heard Tadashi's muted steps across the cold, oak floorboards before he collapsed into his mattress before he himself even thought of actually sleeping. Even when he tried sleeping in Tadashi's bed (encompassed and soothed by his faint scent), he would hear Tadashi give a quiet sigh before retiring on Hiro's side.

The obvious avoidance left him upset, and the brief hellos and goodbyes did nothing more than acknowledge the gaping rift between them. Hiro wanted his Tadashi back. The one who cherished him more than anything in the galaxy. His inspiration. His best friend. His brother.

So, one night, he did the one thing he knew Tadashi could not stand; he went back to the arena.

It must have been his lucky night because big, fat Yama was nowhere to be found. The opponents he did face were incompetent fools (nothing compared to Honey's insane ingenuity, or Wasabi's precise calculations, or Gogo's unstoppable nature, or even Fred's compelling passion). Garbage that slithered forth from the sewers with nothing but thoughts of malice and avarice. Taking that from them gave Hiro no greater satisfaction. (Plus, hey, easy money.)

He escaped with his earnings and barely a nick from the sore losers, but no Tadashi. He should have been tracking him, of that Hiro was sure. He had worn this hoodie specifically for Tadashi to come get him. So why? Why hadn't he come to his rescue? Come to take him home on his Vespa and reprimand him, remind that he was far too intelligent to waste away in those slums.

But there was no older brother waiting. Nothing but a lonely run home to an empty room and a tracking device still hidden within the drawers.

It was still early! Not yet 2 'o clock! Tadashi was probably catching up on all the work he missed.

The lies some people tell themselves.

He needed to make some upgrades to his Megabot anyway. Not that it would serve any purpose against those mediocre fighters. It would be fun, though. Challenging himself to see what he could improve. (Maybe give it super speed and have it race against Gogo!) Or better yet, make a whole army of Megabots!

Make the pain go away.

"Hey! This is Tadashi Hamada. I can't come to the phone right now, so leave your -" Tadashi never turned his phone off.

Tadashi, please...

It was around 5 in the morning when Hiro found himself sunk to the floor, gasping and curling into himself. Cold hands seized his lungs and squeezed the breath right out of his body. Ravenous appendages clawed at him, tore at his throat, left him writhing and burning for air. He couldn't breathe. He couldn't breathe.

Where are you?

Had something happened at SFIT? No. No, no, no. He could hear it, hear those dreadful blares, feel his body aflame with a searing heat, tearing from his a hoarse cry of agony.

"Hello, I am Baymax, your personal, healthcare companion." When had Tadashi brought him home? "My scanners indicate that your adrenaline levels are elevated while the level of carbon dioxide in your bloodstream have significantly decreased. Diagnosis: panic attack."

The scorching heat dissipated beneath the cool, vinyl touch, and the demons tearing at his innards fled. "Recommended care: diaphragmatic breathing. Relax. Inhale deeply through your nose, and exhale through your mouth. Inhale. Exhale."

Inhale. Exhale. Inhale. Exhale.

With each breath, the sirens ringing in his ears died away, and those intense bursts of fear dissolved into nothingness.

"Thanks, Baymax."

"Bed rest is recommended after such a stressful experience."

"I'll keep that in mind. I am satisfied with my care." He watched the robot return to his charging station before he made haste for the doorway, but still careful not to wake Aunt Cass. (She had already done so much for him, for them both, she didn't deserve anymore worries on her shoulders.)

He just had to be at the university; he couldn't be anywhere else.

Even though his lungs burned, even though his calves ached, Hiro kept running. Tore through the deserted streets and alleyways, chased after the few trolleys that were operating at this early hour until he managed to hop aboard one, used every shortcut he had learned (every backyard he'd cut through, every chain-link fence he'd scale) because sometimes he would oversleep and Tadashi had developed the tendency to 'forget' to wake him up.

Not once did he stop until – finally – he burst into their shared lab and collapsed unto the cold tiles beneath him. For once, Tadashi was there. He was working diligently at his station until Hiro's abrupt arrival startled him.

"H-Hiro? What are you doing here so early?"

"You didn't come home," he huffed, too exhausted to move from his place on the floor. He felt sticky and disgusting and in desperate need of his brother's embrace. "I thought something had happened to you." An awkward pause. Then, a broken whisper of, "How could you do this to me?"

He wanted to be held.

"Hiro -"

"Don't touch me!"

He wanted Tadashi to say something.

"Please, calm -"

"Shut up!"

To tell him why...

"Do you have any idea how scared I was? Do you know how I felt? I felt like you'd... Like you'd died! You're never around! You don't want me around anymore? Is that it? Should I just go back to bot fighting? Maybe you'll get lucky and fat ole Yama will -"

Slap!

It didn't hurt, but it did shock him out of his ludicrous rambling. Enough to acknowledge the absolute fright that shone from within Tadashi's brown eyes.

"Never. You never talk like that again, you hear me?" He pulled his younger brother against him, and Hiro felt every shudder, heard every shaky breath, and simply drank it all in. All that he was denied, all that he craved, all that he needed to survive.

He laced his fingers through his brother's short hair and buried his face in the crook of his neck. It was a sentimental pleasure in which he rarely seized the opportunity to indulge.

"Why would you think I don't want you around? Hiro, having you with me, I've never been happier."

"It doesn't seem like it," he murmured against Tadashi's neck. The older one then gently tugged at his hoodie. A tacit call. Look at me, Hiro. The little one obliged.

"I am so sorry. I hadn't even realized. I've been so busy... Hey! You know what, I've been thinking of some upgrades for Baymax. Like his time response to emergency situations."

"So you have been listening."

"Of course! Though, he'd like kind of scary running."

"Are you kidding? He'd look hilarious! Oh! You know what you could do? Give him a sleeker design, with armor! Then he could kick some serious butt if his patient's gonna get hurt!"

"I'm not turning Baymax into a battle bot," Tadashi chuckled, ruffling the younger one's hair and making him pout.

"It's still a good idea."

It still gnawed at him, though; that nauseating feeling, like a lion tearing into his prey. That Tadashi was purposely distancing himself from Hiro. A stupid thought that should have immediately been dismissed in light of his brother's words, yet it overwhelmed him, nagged him to the point where he prevented Tadashi from standing.

"What's wrong? You tired?" The consternation on the little one's face concerned him. "Hey, what's -" The soft yet timid press of lips against his own silenced him. Butterfly kisses peppered his lips to his chin before ending with a single press against his neck where Hiro remained. Surprised, he surely was, but it soon morphed into a fondness as he nuzzled young Hiro's hair and kissed his forehead.

"I thought you were too old for smooches," he teased, ruffling his hair once more. No reply. "Hiro?" He moved him gently, and gave a light laugh at what he found. "All tuckered out, huh?"

Suspicion was truly dangerous. It could lead a person to do crazy things. Like planting a mini GPS device of his own in Tadashi's hat, and bugging the lab where his brother worked so he could keep tabs on everything that went on in there. It wasn't that he didn't trust Tadashi, but he knew the older brother had a bad habit of keeping secrets where (he believed) it benefited Hiro. Never anything devious (like the trackers), but secrets nonetheless.

Like the fact that he had been tinkering with the surviving Microbot. Baymax hovered over his shoulder, watching Tadashi work, then shuffled back a bit to give Tadashi room to work on him.

"OK. That should do it. How's it working, buddy?"

"My trackers are fully functional, but how will being able to track Hiro's tiny robot make me a better healthcare companion?"

'What?'

"Trust me. It will."

Tadashi couldn't be serious. The only reason that the Microbot was acting up was surely because it was just malfunctioning. Damaged irreparably by the destruction of its brethren and the neurotransmitter. It was something that could have and should have been overlooked as a mere fluke.

Yet Tadashi was treating it as something to be tested. Never assume, always be certain. A rule crucial to making any project successful. But why put in the effort for something so trivial?

"Alright, little guy, lead us home." He released the Microbot, watching it fly a ways before grabbing Baymax and trailing after it.

It seemed like he would learn his reasons shortly.

He grabbed his backpack, yelling to Cass that he was going to meet Tadashi.

"Just be back in time for dinner! I'm making my famous hot wings! They'll burn your mouths off!"

"Will do!"

He kept his eyes locked on his wristwatch (wasn't too hard to synchronize it to the chip on Tadashi's hat), tracking his brother's every move.

Not a star in the sky. Even the bright streetlights faded the further he jogged, until he was left in utter darkness, with only the eerie green glow of his watch for guidance. Racing, tracking each swerve and curve that blinking dot made until he finally stumbled across Tadashi.

He had led him to an abandoned warehouse. Its rusted doors chained up tight. Its ancient walls overrun with vines wherever Tadashi shined his flashlight. Busted windows like jagged teeth ready to snatch them up into its deadly confines.

Quickly, he concealed himself, watching as Tadashi rattled the chains of the locked door, and hearing his mutters of frustration when he couldn't unlock it. Baymax – his form slowly inflating once more (probably had to lose some size to fit on Tadashi's Vespa) – motioned to the window just above an old dumpster.

Hiro waited in bated breath as Tadashi ascended Baymax's shoulders and hoisted himself through the open window. Then Baymax followed suit. He chanced closer, only to stop and raise an eyebrow when Baymax excused himself and "let out some air".

"Nice one, Tadashi," he chuckled. Then he looked around. There had to be another way inside. To find out what exactly Tadashi was hoping to discover by following that Microbot. To see what was able to elicit a response from something that should have ceased to function.

An idea struck him.

Hiro sent his Megabot forth, bidding it to disassemble and create makeshift holds for him to climb. He followed Tadashi's steps, and eased his way in through the window. He stood and dusted himself off before walking right into his brother's chest.

"Ta-Tadashi!"

"Just what on Earth are you doing here, Hiro?"

"Wait. You knew I was here?"

"You need to go. I'll catch up." He began ushering Hiro towards the window, but the boy remained steadfast.

"What were you doing with my Microbot?" Even in the dark, he could see his brother's stunned features.

"How did you know about that?"

"Come on! You really thought I wouldn't find out." Hiro glanced around. Its interior was large and smelled of mildew and cold rust, yet alive with the noise of machinery that was clearly out-of-place. Hiro slipped out of his brother's grasp, ignoring his demands. Each step he took atop the rickety landing creaked. He used the dim illumination from his watch as a precautionary measure until Tadashi was gracious enough to use his flashlight.

"Stay close to me," he whispered, clutching at Hiro's sleeve.

They came across a crooked ladder. Tadashi gave it a light kick. It didn't seem dangerous. That didn't stop him from seizing Hiro's hood and yanking him away from it. "Are you crazy?"

Hiro had to roll his eyes. "How could I forget? Ladies first."

"Knucklehead." Hiro ducked to avoid a smack to his head from Tadashi.

"Please exercise caution when wandering around in the dark." They jumped at the sound of Baymax's voice, but heeded his warning.

"We will, bud. Just stay here for now."

Once they were safely on ground level, Tadashi made sure to keep Hiro tucked behind him. The boy chose not to complain, clutching to his brother's cardigan and shying away from the void of shadows swirling around them. The tricks they played on the younger brother's eyes, drawing from him an occasional gasp as he swore he saw something move.

If there was something here with them (stalking them), he'd be damned if he let it touch Tadashi.

Then they saw it. Hidden in plain sight, enormous equipment that mass-produced Hiro's Microbots. The younger one dipped into one of the many barrels, inspecting them, not fully understanding what was going on. Had someone gotten a hold of his designs? No. That couldn't be it. Even if that was the case, the person would be too stupid to piece together the complexity of his creation.

No. Whoever was able to effectively duplicate the Microbots would have had to have analyzed a functioning piece. All – save for the one that was in Hiro's possession – were destroyed in the fire months ago, though. Unless -!

"I knew it," he heard Tadashi quietly murmur. Hiro growled.

That fire was no accident.

Professor Callaghan was murdered.

A soft shuffling of feet came from the darkness behind them, and it snapped Hiro into action. He pushed Tadashi behind him, shielding him even with his small stature, but halted before he barked orders for Megabot to destroy when he saw the plush, marshmallow robot waddle up to them.

"Baymax," he hissed, "you nearly gave me a heart attack!"

"It is a good thing that Tadashi equipped me with defibrillators then. Clear." Both brothers immediately stopped the bot, and Hiro explained that it was merely an expression. Then he was whacked on the head.

"Hey!"

"That was for pushing me."

"I was protecting you! What if it wasn't Baymax?"

"Exactly! You could have gotten hurt."

Upon seeing those dark eyes dilate, Tadashi slowly turned around, watching in awe as the Microbots weaved into a wall of pitch black, silently and seamlessly blending into the shadows.

"Run." He and Hiro took off, but the little one rushed back for Baymax, yanking him forward.

"Why couldn't you make him faster?"

"I had planned on it, but -"

"- got preoccupied with my Microbot?" They squeezed him through a narrow passageway.

"Let it go, Hiro! Besides, we were working on that together!"

Tadashi slid to a halt and shoved aside a crate before following Hiro and Baymax into the underground shaft.

"And you couldn't take a little time to implement it?" Hiro screamed as the bots burst through, obstructing their pathway and forcing them to quickly alter routes. The younger Hamada raced for the door, yanking at it as if it would magically unlock. "Punch it, Baymax!"

"He's not made for that, Hiro!" Tadashi might not have been able to see those little devils, but he could surely hear them. He shined his light on Hiro and he nearly dropped it, for hovering menacingly above little Hiro was a hand constructed from those lethal creatures. The little one followed the trail of light, arms flopping to his sides as he watched the hissing metal descend in frozen horror.

Racing forth, Tadashi knocked him out of the way just in time for the makeshift hand to grab his leg instead. Its mighty grip tightened, slowly crushing the trapped appendage. The elder brother bayed in agony.

Snap!

He slammed his fists against them. Dent it! Destroy it! Anything! Just protect Hiro!

So, they thought they could hurt his Tadashi and get away with it?

Bitter yells of, "Run away, Hiro!" quickly morphed into wordless whimpers and groans.

That simply wouldn't do.

The boy knelt down and opened his backpack. From its contents, he pulled out a simple, silver headband. Testing prototypes was so tedious, but – hey – there was no time like the present.

A quiet order of, "M-bots. Destroy," was all Tadashi heard before the painful constriction surrounding his leg was gone.

There were dozens of them scurrying around. Robots half the size of the original Megabot that worked in tandem with one another, combating the onslaught of Microbots for the sake of defending their creator. Either they tore apart the monsters they faced, or were torn apart themselves, and – even then – the dismantled pieces joined the frenzy.

"Baymax, scan!" Hiro ordered as he pulled the health bot towards his brother. Luckily, Tadashi was unharmed from that assault. Only some minor bruises and soreness. "Great! Let's go, Tadashi!"

The M-bots bought them enough time to get back up the ladder. He let Hiro slip out first before readying to push Baymax out.

It was by chance that he saw the yellow eyes of the demon's mask leer at him through the darkness. Waves of Microbots rose and curved behind him, undeterred by the counterattack, and ready to pierce through both himself and Baymax.

Tadashi never ran so fast in his life, hitting Baymax with such force that it sent them flying through the window. There was a brief sensation of free fall followed by the vague realization that hitting the ground from this height was not going to end well. Then he was enveloped in Baymax's strong embrace as the nurse bot took the brunt of the impact.

Hiro called his brother, shaking him from his stupor before directing both him and Baymax toward his Vespa.

"Baymax! I am satisfied with my care!"

"Megabot, come on!" There was no need to get the others; there was nothing left to retrieve. The original returned to its master's side just as the bots burst through.

"Hiro, get on!" Tadashi slipped Baymax's now compact design unto the base of his Vespa, and wasted no time speeding off once he felt Hiro's slim arms wrap around his waist.

Tadashi was so transparent. He may as well have been screaming his thoughts at the top of his lungs.

'That man killed Professor Callaghan! He stole Hiro's bots! He attacked us! He tried to hurt Hiro!'

But he didn't. Just kept it bottled up inside. So typical of his brother. Always trying to be strong, trying to silently shoulder the burden that this pain left in his heart, trying not to worry his baby brother, who he didn't know was already ten steps ahead of him. Thinking, planning.

The police would be of no use in this case. A man wearing a kabuki mask attacking them with Hiro's presumably destroyed Microbots? They might throw them both in the loony bin if they heard that story.

He had to think of something quickly, though. Hiro couldn't let this upsetting revelation impair his brother's judgment. Make him do something that got himself hurt; make him decide to play the martyr for the sake of justice on Callaghan's behalf.

Now that wouldn't do at all.