The stairway descended farther than Ren expected.
Each step echoed softly, swallowed by the darkness below. The air grew colder with every meter they moved downward, carrying a sterile scent that reminded Ren of hospitals and sealed laboratories. The faint hum of machinery vibrated through the walls, subtle but constant—like the building itself was alive.
Aiko walked just ahead of him, her pace steady but cautious. She didn't look back, yet Ren could tell she was tense. Her shoulders were stiff, her grip on the railing firm.
Neither of them spoke.
At the bottom of the stairway, a reinforced metal door awaited them. No handle. No keypad. Only a circular scanner embedded into the surface.
Mr. Sashimoto stepped forward.
The scanner glowed blue.
The door opened silently.
Ren's breath caught.
⸻
The laboratory beneath Kurogane Science Academy was nothing like the classrooms above.
Wide, circular in shape, it stretched farther than Ren could see at first glance. Transparent panels lined the walls, each displaying flowing data—genetic sequences, cellular structures, energy readings that updated in real time. Massive cylindrical chambers stood upright at regular intervals, their interiors dark and unreadable.
The ceiling was high, crisscrossed with steel beams and thick cables that pulsed faintly with light.
"This…" Aiko whispered. "This is under the school?"
Mr. Sashimoto smiled faintly. "Knowledge is safest when hidden in plain sight."
Ren's instincts screamed at him to analyze everything at once, but there was too much—too advanced. Equipment here rivaled government research facilities. No… it exceeded them.
"This place doesn't belong to a high school," Ren said carefully.
"Correct," Mr. Sashimoto replied. "The school belongs to this place."
Ren stiffened.
⸻
"You're probably wondering why you're here," Mr. Sashimoto continued, walking toward one of the illuminated panels. With a simple gesture, the display shifted, revealing a rotating three-dimensional model of a human body.
"Humanity," the teacher said calmly, "is flawed—not morally, but structurally. We are bound by biological limitations that no longer suit the world we inhabit."
The model zoomed in on DNA strands, twisting endlessly.
"Arcadia's citizens broke past those limits," Aiko said quietly.
Mr. Sashimoto turned toward her, eyes sharp with interest. "An excellent observation, Nakamura."
Ren glanced at her in surprise.
"They defy physics," Aiko continued. "But not randomly. Their abilities follow patterns. Rules."
Mr. Sashimoto's smile deepened.
"Exactly."
Ren's pulse quickened.
"You've studied Arcadia?" Ren asked.
"Observed," Mr. Sashimoto corrected. "Analyzed. Learned."
He tapped the panel again. The display shifted—energy waves overlapping with genetic structures, highlighted in brilliant light.
"There is a threshold," the teacher said. "A point at which the human body stops rejecting change… and begins adapting to it."
Ren's throat tightened.
"A threshold?" he repeated.
Mr. Sashimoto turned to face him fully.
"A gamma threshold."
The words settled heavily in the room.
⸻
A low mechanical sound filled the lab.
One of the cylindrical chambers came to life.
Lights flickered inside, revealing a humanoid silhouette suspended within translucent fluid. Tubes and cables connected to the chamber, feeding data into the surrounding systems.
Ren took a step back without realizing it.
"What… is that?" he asked.
Mr. Sashimoto's voice remained calm. "A failed subject."
Aiko's eyes widened. "Failed?"
"Yes," the teacher said casually. "The body rejected evolution."
Ren felt his stomach twist.
"Was it a student?" Ren asked.
The silence that followed was answer enough.
⸻
"You brought us here to show us this?" Ren said, struggling to keep his voice steady. "Why?"
Mr. Sashimoto approached him slowly.
"Because you think before you act," he said. "Because you understand restraint. And because your mind seeks solutions, not destruction."
Ren clenched his fists.
"And her?" he asked, nodding toward Aiko.
"She observes what others overlook," Mr. Sashimoto replied. "Pattern recognition is rare."
Aiko didn't look away.
"And Kaito?" she asked suddenly.
Mr. Sashimoto paused.
"Ah," he said. "Moriyama will come later."
Ren didn't like the way he said that.
⸻
"I am not asking you to decide anything today," Mr. Sashimoto continued. "I am merely offering you knowledge."
He gestured toward a smaller console near the center of the lab.
"Sit," he said. "Observe. Ask questions."
Ren hesitated.
Then he sat.
As data streamed across the screens, Ren felt something strange stir within him—not power, not fear, but possibility. The equations weren't complete, but he could see the gaps. The inefficiencies. The risks.
And the potential.
If refined…
If controlled…
This could end wars.
Aiko leaned closer to one of the displays, eyes reflecting streams of genetic code.
"Sensei," she said quietly, "if this succeeds… what happens to the world?"
Mr. Sashimoto looked at the suspended figure in the chamber.
"The world adapts," he said. "Or it is left behind."
Somewhere deep within the facility, a warning light flickered—unnoticed.
And far above them, ordinary students laughed, unaware that beneath their feet, humanity stood one step closer to crossing the gamma threshold.