"Your legs are trembling."
The statement came from the lips of another man.
Kevin stood beside Kosma with his arms crossed and ordered in a commanding tone, "Leave this place. The storm is about to arrive."
"I know..." Kosma did not look up. He kept his eyes fixed on the tornado drawing closer in the distance. "The enemy is going to attack here. I have to protect the people behind me."
"Because I am the hero Shadow ★ Shine. Shadow ★ Shine never turns his back on the enemy—only on those he must protect."
Kosma understood the vast gap between himself and the Fourth Herrscher. According to the information from that chuunibyou older sister, the opponent could casually summon hurricanes, while he himself would probably be crushed with a mere flick of her hand.
But so what? This was the fate of a hero. Shadow ★ Shine was the dawn of the city—the hero who brought hope from impossible despair.
"And you? Are you my enemy?"
Kosma did not know Kevin's stance, but his instincts told him this cold-voiced man was an ally.
...
"Your spirit is admirable, but willpower alone cannot defeat a Herrscher."
The firm words descended from above, prompting Kosma to raise his head and look at the man before him.
That gaze pinned Kosma in place.
It was the gaze of someone prepared to die.
It was also the gaze of someone who would overcome everything.
It was a gaze Kosma himself did not possess.
This man's resolve was beyond that of ordinary people.
If Kosma was still wavering on the path of choosing to become a hero, then this man had already cast aside hesitation and choice.
If Kosma was striving to become a hero, then this man was already advancing down that road.
"Shadow ★ Shine, is it? A fitting title for you."
The man dropped the metal case to the ground with a heavy thud. It was hard to imagine what kind of weight he had been carrying.
"You're a good kid. So... live, all right?"
Kosma knew that the cold man before him was a true hero.
...
Kevin watched Kosma leave. It was only to be expected. The boy's body had been trembling like a tiny electric motor.
For a child to stand here alone for so long already counted as remarkable courage—even by adult standards.
There was no shame in retreating, because Kevin had taken on his responsibility. That had always been the duty of a MOTH soldier. It should never have been borne by a ten-year-old boy, even if Kevin himself was only eighteen.
Becoming a hero was not about seeking death.
The boy had a clear understanding of himself. Yet there had been a certain light in his eyes that even Kevin found difficult to face. That light granted him the courage to stake everything on one desperate stand.
"Not a bad kid. I hope we meet again someday."
Kevin had a feeling that someone like that would never remain obscure in the face of the Honkai. Sooner or later, he would rise above the rest and become a shining new star.
Before leaving, Kosma had given Kevin an unexpected piece of information: this Herrscher might possess the ability to manipulate ideal fluids.
Kevin had no idea where the boy had obtained such intelligence.
...
Mobius' laboratory.
Dr. Mobius was busy popping bubble wrap.
"Doctor, a frontline report from Kevin... Dr. Mei's little follower."
The research assistant Klein projected Kevin's message onto the massive display screen in the lab.
In Dr. Mobius' eyes, few people were worth remembering by name, so Klein used Mobius' usual way of referring to Kevin.
As one of the founders of MOTH, Mobius naturally paid close attention to the war against the Herrscher. That was precisely why she was popping bubble wrap.
Dr. Mobius frowned in confusion. "Creating and controlling ideal fluids?"
"Is there a problem, Doctor?" Klein did not grasp the deeper implications.
Mobius spoke in a testing tone. "Do you know what an ideal fluid is, Klein?"
"Of course. An ideal fluid, also known as an inviscid fluid, is a hypothetical fluid that produces no internal friction during flow. In other words, its viscosity is zero." Klein recited as though quoting a textbook.
"Correct. Inviscid, incompressible, produces no heat, and has zero vorticity. Those are the characteristics of an ideal fluid."
"Do you know what a perpetual motion machine is? An ideal fluid is precisely that. And it can turn anything it touches into a perpetual motion machine as well."
"What does that imply, Doctor?" Klein clearly had not realized how terrifying such a concept could be.
"An ideal fluid is romance that exists only within scientific ideals. When the romance of scientific ideals enters reality, it often brings nothing but catastrophic disaster."
Mobius set aside the tattered bubble wrap and drew two parallel lines on the screen.
"These are streamlines of matter, Klein. Imagine them as water. When an object passes through, what happens?"
"It produces vortices and resistance, Doctor."
"Exactly. Then what if there are no vortices and no resistance?"
Klein closed her eyes and shook her head. "I can't picture it..."
Because that already lay beyond the scope of all current theory. According to existing models, ideal fluids were nothing more than theoretical tools.
By modern theory, such a substance could not possibly exist in reality.
Rather than a substance, it was more like an intangible concept.
Seeing Klein's confusion, Mobius chuckled and tapped lightly on the screen again.
"This is the result, Klein. Ideal fluids are not harmless little turtles from textbooks that shy away from everything they encounter."
"If the streamlines of matter remain unchanged, then any object obstructing them will be subjected to boson-level—or even higher—shearing, reduced into a quantum state devoid of size and structure, impossible to observe. Not even a black hole could escape being sliced apart."
"But... Doctor..."
"Hm? What is it, Klein? Do you have another question? Or do you not understand why it becomes a quantum state?"
"Doctor, what I meant to say is... you drew a turtle on the screen."
Dr. Mobius curled her lips playfully and replied lightly, "That's not important, Klein. No one ever stipulated that the graph on coordinate axes must be linear or nonlinear experimental data."
At that moment, a glaring red warning suddenly lit up at the bottom of the large display.
Mobius' eyes sharpened. She swiftly swiped her slender finger across the screen, switching to another instrument's monitoring channel.
It was a device conducting real-time monitoring of a certain lifeform.
The subject under observation was a robust man—though perhaps he could no longer be called human.
Most of his body had already transformed into silicon-based cells of a Honkai Beast. His metabolic cycle differed entirely from that of a human. He could even stimulate his own cells to alter his lifeform.
Just as the screen now displayed, he was stimulating the cells in his hand to transform them into massive pincers, while altering the cells in his face into a mask.
"Experimental Subject CMB-001. Looks like you've recovered quite well. You can even escape from my laboratory now. Blanca's friend certainly knows how to cause me trouble..."
Mobius picked up a fresh sheet of bubble wrap and angrily popped several bubbles.