Amatsu sat in silence, the flickering glow of distant fires casting long shadows against the damp walls.
To become stronger was to understand.
Strength was not merely an accumulation of power. It was comprehension—an intimate knowledge of the forces at play. The deeper his understanding, the more efficiently he could wield his evolution. For two weeks, he had hunted alongside Eto, tearing through the starving and the desperate. Every kill refined him, every battle carved new lessons into his mind. He could feel himself changing, sharpening—but how much?
The question gnawed at him.
Amatsu knew the basics. Rc cells dictated a ghoul's strength. The denser they were, the more powerful the ghoul became. This much was obvious. He had felt the gradual thickening of his own Rc density, his kagune growing more responsive, more alive with every meal. The Serpent understood this too, whispering its silent knowledge through the marrow of his bones. The more he consumed, the more clearly he could perceive these changes, each bite revealing details he hadn't noticed before.
Recent hunts had given him useful data. Starving ghouls crumbled before him, their flesh weak, their movements sluggish. He had surpassed them. That much was certain. But he needed more than certainty—he needed precision.
He closed his eyes, letting the numbers unfold in his mind. Human Rc cells. Ghoul Rc cells. The fluctuation of strength, the limits of starvation. He sifted through it all, eliminating inconsistencies, honing in on the truth.
Silence.
For half an hour, he did nothing but think.
A normal human possessed Rc cells, but in pitiful amounts—perhaps 500 per milliliter of blood, fluctuating based on genetics. Weak, inconsequential. Starving ghouls, however, presented a more interesting case. When deprived of sustenance, their Rc count dropped, their bodies shriveling, their kagune barely manifesting. At their weakest, they were only marginally stronger than humans.
His estimate: 800 to 1,500 Rc cells per milliliter for starving ghouls. Still above humans, but fragile, brittle. A state of diminishing returns.
But Amatsu wasn't starving.
He opened his eyes. A slow breath. His fingers curled slightly, feeling the hum of Rc cells coursing beneath his skin. The Serpent stirred, sensing his focus, coiling with anticipation.
He was not like them. He was feeding. Growing. Adapting.
And if he could quantify his growth, understand its increments, then he could control it.
Hunger alone did not make one stronger. That was the mistake of lesser ghouls. They devoured mindlessly, hoping strength would come through sheer consumption. Amatsu would not rely on chance.
He would refine himself with purpose.
Every kill was a data point.
Every hunt, an experiment.
Every evolution, a calculated step toward something greater.
Yet, something unsettled him.
There were gaps in his understanding. Outliers. Unexplained anomalies in the Rc balance. He had killed ghouls that should have been weak—starving, brittle things—and yet their Rc cells surged unnaturally at the moment of death, as if resisting their fate. Others had fractured instead of dissolved, their flesh refusing to break down properly, their cells reacting in ways he couldn't yet decipher.
And then there were those that changed.
Rare cases. Ones who, in their final moments, did not simply die but became something else. Their Rc patterns twisting, spiraling into forms that defied his calculations. The Serpent had noticed too, recoiling in wariness, as if recognizing something beyond its hunger.
Mutation. Evolution. A path not yet understood.
For now, it was only a whisper of a thought. A question without an answer.
But Amatsu would find it.
Because to become stronger was to understand.
And he would understand everything.
Amatsu sat across from Eto, the dim glow of phosphorescent fungi casting eerie shadows on the cavern walls. Eto was perched on a broken slab of concrete, swinging her legs absently, but her eyes were sharp, reflecting amusement and curiosity.
"So," Amatsu began, his voice quiet but precise, "Rc cells. They dictate a ghoul's strength."
Eto tilted her head. "Sure, but that's obvious. What about them?"
"I want to quantify them," he said. "If strength is dictated by Rc cell density, then there must be an average range."
Eto blinked, then grinned. "Ohhh, now that's interesting. You want numbers?"
"Yes."
She considered it, gaze flicking upward. "Well… I've never thought about it like that. But let's see. Starving ghouls are weak, barely able to keep their kagune out for long. Their Rc cells must be really low."
"800 to 1,500," Amatsu supplied. "At least, from what I've observed."
Eto's grin widened. "You already figured that out? Damn. Alright, let's play this game." She tapped her chin. "A normal, well-fed ghoul—one that isn't wasting away—should be a lot higher than that. Maybe around… 3000,? 4,000?"
Amatsu nodded. "That makes sense. The ones we've been fighting—those that weren't starving but still weak—they felt somewhere in that range."
"What about stronger ghouls?" Eto asked, now fully engaged. "They should be way past that."
He thought about it. The ghouls with refined kagune, efficient movements, a presence that wasn't just instinctual hunger but true power. "8,000. Maybe 10,000."
Eto whistled. "Then where do you fall?"
He already had the answer.
He had felt the difference, the ease with which he tore through his prey. His kagune didn't just manifest—it surged, dense, refined, growing stronger with each hunt. He wasn't at 2,000. He had surpassed that. He wasn't merely feeding—he was evolving.
He met Eto's gaze. "4,200."
A beat of silence. Then Eto threw back her head and laughed. "Holy shit. You're creeping into Vulture territory strength." She leaned forward, eyes glinting. "Are you sure you're only ten?"
Amatsu didn't respond to the tease. He had his answer. And now, he had something even more valuable—a baseline.
He wasn't just growing stronger.
He could measure it.
And that meant he could control it.
Eto's laughter still echoed off the walls when Amatsu shifted his weight forward, eyes sharpening in the dim glow.
"Vulture territory," she had said.
An interesting benchmark—but not the ceiling.
Eto grinned at him, her feet swinging lazily from the broken concrete slab. "So, number. What's next?"
"Verification."
Eto blinked. "Huh?"
"I have an estimate of my Rc count," Amatsu said, voice calm, deliberate. "But estimates aren't proof. And proof is power."
A slow, creeping grin spread across Eto's face. "Ooooh. You wanna test it?"
Amatsu nodded once. "Against something measurable."
Her expression turned thoughtful. Then, abruptly, she hopped off her perch, stretching her arms over her head like a cat. "Lucky for you, I know exactly how to do that."
She turned, gesturing for him to follow, her mismatched eyes gleaming. "Come on. I know where we can find something strong enough to measure yourself against."
-
The tunnels twisted and stretched, damp air pressing in from all sides. The deeper they went, the quieter the world became.
Amatsu followed Eto in silence, eyes scanning the walls—scratches, remnants of blood, discarded bones stripped clean. A place where things starved and things fed.
He could hear them before he saw them.
Labored breathing. Shuffling movements. A faint, wet sound—like something chewing with mechanical patience.
Eto stopped, pressing a finger to her lips. Then she pointed toward a jagged opening in the rock. The scent of old blood drifted through, thick and metallic.
"A small hunting pack," she murmured. "Two, maybe three."
Amatsu could already see the shapes moving inside. Their bodies were skeletal, but not fragile. Not like the ones they had crushed over the past weeks. These ones still had weight, despite their gauntness. Their Rc cells weren't spent—they were controlled, refined.
A different kind of survivor.
Eto leaned in. "Vulture Scavengers. Tougher than your average starving ghoul. Smarter, too."
She smirked, tilting her head. "Perfect for measuring yourself against, don't you think?"
Amatsu didn't respond.
His kagune lashed out—two thick, serrated tails slicing forward with a whiplike crack. The nearest scavenger barely had time to turn before the first tail slammed through its ribcage, puncturing flesh with a wet, sucking sound.
A gurgled shriek.
The others snapped to attention, muscles coiling, eyes burning with sudden, feral clarity.
For a split second, the tunnel was frozen.
Then they lunged.