As a scientist, and one who'd spent years buried in Gastrea Virus research, Sumire understood exactly what his words meant.
The Gastrea Virus was the most terrifying, least controllable thing on the planet. It ate through human bodies, seized human minds, and left monsters where people had been.
For decades, countless researchers had thrown themselves at it, hunting for a way to control it or purge it. Nobody had ever broken through.
And now he was telling her he hadn't been infected at all. He'd taken hold of it. Pinned the corrosion rate at ten percent with no side effects whatsoever. Maybe that wasn't total mastery, but the difference hardly mattered.
If the method could be isolated, if it could be copied into the Cursed Children, then every last one of them would be free of the virus. Every one of them would have a future.
The rate could even be raised deliberately, amplifying their strength while stripping away the cost. Or handed to people who'd never carried it at all.
This wasn't only her dream of the last decade. This was the world's way out.
He watched her come apart at the seams and offered a mild smile, one shoulder lifting in a shrug, tossing it off like a weather report.
"You're overselling it. All I did was cap it at that level and cut out the side effects."
"Overselling it?"
Her voice climbed. She stared at him, eyes wide, disbelief and exhilaration crowding each other out. "Do you have any idea what you're saying?"
"Holding the Gastrea Virus corrosion rate at a fixed number, with no side effects at all. Do you understand what that means?"
"It means you've cracked the virus. It means every Cursed Child can be saved. It means this world, after decades of being hunted by Gastrea, finally has a way forward."
Her voice broke on the last word. Her hands trembled where they hung at her sides, and her eyes burned with a hunger for the answer and everything it promised.
His smile stayed gentle.
"So," he said, teasing, "would you call that a surprise now?"
"A surprise? This goes far past a surprise. This is a miracle."
Whatever composure she had left snapped. She grabbed a fistful of his collar, staring up at him, her voice cracking like she might burst into tears.
"The laboratory."
"The lab you promised me. When do I get it?"
Only one thought occupied her now: drag him into a laboratory, take his body apart piece by piece, study whatever enhancement he was carrying and work out how to replicate it.
She couldn't wait. She wanted to start this instant, break the virus open this instant, save every one of those girls.
"That part's out of my hands, I'm afraid."
He eased her fingers off his collar, an apologetic tilt to his smile. "Seitenshi's already making arrangements. These things take a little time."
The delay chafed at him too. Nothing moved until the lab existed, and until it existed Sumire couldn't work, and until she worked the children stayed where they were.
But building a facility capable of handling Gastrea Virus research meant funding, equipment, staff, security. Even Seitenshi needed time.
"I don't care."
Frustration bled through every word. "Then you shouldn't have told me. Why tell me now, with no lab to work in?"
"It's like a thousand cats clawing at the inside of my skull. Do you understand that? I want to start now."
She'd found the treasure and couldn't get the lid off the chest. The wait was going to drive her out of her mind.
"I wanted to share the joy with you."
The grin that spread across his face was pure mischief. He'd done it on purpose and made no attempt to hide it.
He'd wanted to see what this perpetually cool, perpetually rational scientist looked like when something big enough came along to crack her open.
Her teeth ground together. The urge to smash the analyzer straight into that smug face rose up and had to be wrestled down.
He was her employer, the source of her funding and her freedom. More than that, he was the only specimen of his kind anywhere in the world, the key to the whole thing. She needed too much from him to burn the bridge.
"Sharing the joy. Right."
She shot him a sour look and let it drop, though the exasperation in her voice said plenty on its own.
Watching her puff up like that, he let the teasing go and dropped the smirk. His tone shifted.
"All right, I'll stop. The joy's been shared. Time to work."
Ignoring the reproachful glare aimed at him, he reached over and took the notebook from her hands, the one holding every child's corrosion rate.
He turned the pages one by one, and the smile faded off his face as he read.
Because none of these numbers were low.
They weren't like Enju, locked in constant combat with Gastrea, facing the threat head-on day after day. Their rates climbed slowly by comparison.
But slow accumulation over years still accumulates. The totals had crept somewhere unpleasant.
His brows drew tighter as he scanned down the columns.
Several of them had already passed forty percent. One step from the fifty percent line.
Cross that line and there was no coming back. No reason left, no self, only the thing the virus made of them.
Looking at the cold figures, something in him settled into gratitude.
He'd arrived in time. He'd redeemed the Gastrea Virus enhancement in time. He'd chosen to start with the children themselves instead of the world around them.
Left alone, those girls above forty percent had a short road ahead. One night, not long from now, each would slip out of the sewers alone, find somewhere empty and quiet, and end it.
They wouldn't want to become Gastrea. Wouldn't want to hurt anyone. So they'd choose the cruelest exit available and close out their short, painful lives with it.
The thought left an ache behind his ribs, and his eyes hardened.
Sumire had to find the replication method, and fast. These children were going to be free of the virus. They were going to grow up the way children were supposed to, laughing, healthy, with something bright waiting at the end of it.
He remembered the little notebook Elder Matsuzaki had shown him: names, ages, corrosion rates. And the entries for the ones whose numbers had climbed too high, who were no longer here.
Drawing in a breath, he pushed the ache down, closed the file, and turned to where the old man stood with confusion still written on his face.
"Elder Matsuzaki, could you gather the children? There's something I need to tell them."
The old man blinked, then nodded. He had no idea what this was about, but his trust in Satoru ran deep.
Watching him walk away, Satoru turned it over in his mind.
Enju had spent her life fighting alongside Rentaro, standing against Gastrea. These girls in the sewers were built differently. Timid, most of them. Easily frightened.
Loathed and driven off since infancy, carrying more injury than any child should, they met anything unfamiliar with fear and a readiness to flee.
Announcing outright that he intended to lower their corrosion rates, then reaching into their bodies to rewrite the virus inside them, would terrify a fair number of them. Some would refuse outright.
Better to come at it sideways. Something they could accept. Something they could understand.
"I'm going to lower their corrosion rates."
He said it plainly, meeting the old man's eyes.
Matsuzaki went blank. His eyes widened, disbelief flooding his face, and he repeated it under his breath.
"Lower the corrosion rate?"
"That... that can't be done."
He'd understood every word individually. Strung together they made no sense at all.
Lower it? The phrase sat wrong in his ears. He'd lived a long life, met more Cursed Children than he could count, met more scientists than he cared to, and not once had anyone suggested a corrosion rate could go down.
Even the most expensive, most effective Suppressant only slowed the climb. Nothing reversed it.
If reversal were possible, there wouldn't be a fresh crop of children every year turning into Gastrea or walking off alone to end things.
He swallowed the questions and nodded, then strode off toward the children at their games and began calling them together.
They broke off one by one at his voice and formed a small ragged line, drifting over toward Satoru.
Curiosity lit every face. None of them knew what was coming.
They gathered in front of him in a loose circle, chins tipped up, small faces turned toward him and waiting.
He looked over them, all those young open faces, and his expression softened. He raised a hand and beckoned to Aii.
"Aii, come here. Help me show everyone a magic trick, would you?"
She had no idea what he meant. Her big eyes blinked once. Then she caught the warmth in his smile and nodded without a second's hesitation. "Okay!"
"What do you want me to do, mister?"
Whatever he asked, she'd agree to. Anything at all, so long as it helped him, made her happy.
He bent down, close to her ear, pitching his voice for the two of them alone.
"Same as last time, when I fixed your eyes. This time I'm going to lower everyone's corrosion rate. It might sting a bit, and it might look a little scary. If you get frightened, hold on to my hand. Deal?"
The process might be uncomfortable, and he wanted her prepared for it.
He also wanted her to go first. Let the rest of them watch, see there was nothing to fear in it, and come forward on their own.
Her eyes brightened. She shook her head hard, and something brave settled into her face. "It's fine, mister. Aii isn't scared of a little pain."
"And you're so kind. Even if it does hurt, it won't hurt much. Aii isn't scared."
She reached out and wrapped her small warm hand around his fingers, gripping tight, trust and resolve in every line of her.
Something in his chest went warm. He patted the back of her hand.
"What a brave girl."
Then he straightened and turned to the ring of children around him, his voice easy and kind.
"All right, everyone. I'm about to show you a piece of real magic."
"This trick means none of you ever have to worry about turning into a monster again. It means you all get to grow up healthy and happy. How does that sound?"