Reincarnated as The Greatest Scientist in Another World

Zuko stepped out of Ain's creaking hut, the brittle bamboo door sighing shut behind him. The heat of midday clung to his skin, yet there was a fire inside him now that no sun could match. Ain's fierce eyes, his crude notes, his trembling mother — it all lit a fuse Zuko hadn't known was still buried in his chest.

He sucked in a deep breath, trying to steady his heartbeat. That was when he saw her: a small girl trudging along the muddy lane toward Ain's hut, shoulders hunched, hair limp and matted. Nasuha.

Zuko paused. He knew that face too well. That night — the High Council's carriage rolling past his window, the muffled cries, the mages' wine-soaked laughter dragging Null girls through the brothel's back door. He had seen her then, her eyes glassy under torchlight.

He shook his head, chasing the poison from his veins. Not now.

"Hey," he called, forcing a smile as he stepped closer.

Nasuha froze. She looked up — and for a heartbeat, her wide eyes didn't know him. Then they dropped to his cloak's gold trim, the remnants of noble polish still clinging to his battered clothes.

Her breath caught. The world seemed to crush her as she stumbled back, thin knees giving way. She hit the mud with a wet smack, arms hugging her chest like she could hide what had already been stolen.

"No! Please! I didn't— I won't—" Her voice cracked into a hoarse sob. She trembled so violently that the dirty scarf slipped from her hair.

Zuko's hands flew up. "Wait— no! I'm not—"

He knelt, reaching to help her — but before his fingers could brush her shoulder, something slammed into him. Ain shoved him back, planting himself between Zuko and the girl.

"Don't," Ain growled, his eyes cold as iron gates.

Zuko held up both hands, palms open, words drying in his throat. Nasuha pressed herself to Ain's side, face buried in his threadbare tunic, her shoulders shuddering with sobs that made no sound.

Ain's voice cut through the hush, sharp but low enough for only Zuko to hear. "You think she wants your noble hands on her? Look at her, Zuko. She's not afraid of you. She's afraid of what you wear."

Zuko's chest clenched. He looked at her — really looked — and saw the bruises beneath her sleeves, the raw terror tangled like barbed wire behind her eyes.

He couldn't breathe.

Ain's mother appeared at the hut's doorway, arms open just enough for Nasuha to collapse into them. Ain gave the girl one last glance before he turned that same frost onto Zuko. "Leave her be."

Zuko stood there, rooted, then stepped back wordlessly. His boots squelched through the mud as he walked the narrow path away. The slum sprawled around him like an open wound — rotting huts, hollow faces, children fighting over stale crusts.

How did they breathe here? How did they keep breathing when this was all they'd ever have?

Ain's voice cut through his haze. "Zuko—?"

Zuko spun, grabbed Ain's arm so hard his fingers dug to the bone. Ain jerked to pull free, but Zuko held him there, eyes blazing.

"What the hell are you doing?" Ain hissed.

"Something you can't do alone," Zuko shot back. "You want to change this? Then come with me. Right now."

Ain's brow furrowed. "Where? Into the city? You want me dead? If they see me past the gate, they'll skin me for sport."

Zuko's lip curled into a half-mad grin. "Not if you're with me. I still have the name Hearthfilia sewn into my throat — and I'll bleed every shred of it dry."

Ain hesitated, glancing back toward the hut. Nasuha's muffled sobs bled into the heavy heat.

He turned back. "Fine. But if you get me killed—"

"Save your curses," Zuko barked. "You'll need them for the nobles."

---

They marched down the dirt lanes toward the massive iron gates that split the Null slums from Holy Stone proper. Towering walls loomed overhead, crowned with spears and rows of enchanted crystals pulsing faint blue — enough mana to burn a hundred Null to ash.

Five armored knights lounged at the gate, half-asleep in the heat. The moment they spotted Ain, they stiffened — snarling like dogs scenting a rat.

"Stop right there!" The lead knight barked, spear point leveled at Ain's chest. "Nulls don't cross. Drag him back—"

Zuko stepped forward, drawing a velvet pouch from his cloak. It jingled with the promise of gold. He tossed it — the knight caught it midair, eyes flicking between the coins and Zuko's calm smirk.

"House Hearthfilia business," Zuko said lazily. "He's with me."

The knight spat near Ain's boot but stepped aside. "Five minutes. If that thing runs—"

Zuko clapped the man's shoulder so hard his armor rattled. "He won't."

---

Inside the gate, Ain froze. He'd seen the city from afar — the polished towers, the lamps that flickered to life at dusk. But to stand here, on sunlit cobbles, felt like stepping into a lie so pretty it could kill.

People stared. Zuko strode ahead, chin high, while Ain trailed behind — each muddy footprint drawing gasps and curled lips. Perfumed ladies lifted silk hems to keep his dirt from their shoes. A merchant grabbed his son's arm and jerked him away. A man pinched his nose dramatically and spat at Ain's feet.

Zuko ignored it all. He marched Ain to a grand wooden building ringed with steam. Gold letters above the door read: Jasmine Springs — For Gentlefolk Only.

Ain balked. "What is this—?"

Zuko grabbed his shoulder and shoved him through the doors. Inside, warm, perfumed steam curled through marble halls. Attendants froze when they saw Ain.

"A Null?" one whispered, scandalized. "Get him out—"

Zuko slammed a handful of gold onto the marble counter. "He bathes. Now."

Silence. Then, grudgingly, the attendants guided Ain past rows of marble pools, each steaming with spring water. Nobles gawked as Ain stripped his ragged shirt and lowered himself into the heat. Gasps. Hisses. But no one dared touch him — not with Zuko watching.

For the first time in his life, hot water kissed Ain's skin. Filth he thought permanent slipped away in greasy streams. He scrubbed until his skin stung raw. Zuko lounged on the pool's edge, kicking water at him like a smug older brother.

"You look like a half-drowned dog," Zuko laughed.

Ain flicked a handful of water back. For a heartbeat, the slums felt far away.

---

They left the bathhouse only for Zuko to drag Ain into a cramped barber's shop. Clumps of matted hair fell away in silent heaps. Beneath it emerged sharp eyes, a clean jaw — a boy no longer hidden under years of grime. The barber worked quickly, glancing nervously at Zuko's gold.

Next came the tailor's stall. Linen shirts, sturdy boots, a simple brown coat that made Ain look like an apprentice — not a Null to spit on.

Ain caught his reflection in a brass mirror and barely knew the boy staring back.

---

They finished at a general store near the city gate. Zuko bought sacks of rice, barrels of clean water, dried fish, bolts of cloth — enough to fill ten ox-carts. The shopkeeper nearly fainted when Zuko dropped a pile of gold on the counter.

---

When they returned to the slum gate, the same knights gawked at the mountain of supplies.

Zuko shoved another pouch into the lead guard's hand. "Open it."

The iron gate swung wide again.

---

Back in the Null slum, word spread like fire. Ain and Zuko stood atop the carts, tossing bundles of rice and fresh cloth to mothers, the barefoot, the forgotten.

Children who once fought over moldy crusts now laughed with sticky rice smeared on their cheeks. Mothers wept over blankets warm enough to keep babies breathing through the night. The hopeless eyes of the old flickered with something fragile — trust.

When the last bag was gone and dusk settled over the crumbling roofs, Ain sat beside Zuko on the edge of an empty cart. The air smelled of bread, steam, and something that almost tasted like hope.

He looked at Zuko, voice barely above a whisper. "Why? Why do this? You're a prince. Why pretend to care?"

Zuko didn't answer at first. He just watched the children run barefoot through the mud, new shoes clutched tight in tiny hands.

"I'm not pretending," he said at last. "I'm just trying to remind myself people are people. Even when the palace forgets."

He turned, met Ain's eyes, and the ghost of a grin tugged at his lips.

"I'm just trying," Zuko said, "to make humans human again."