Chapter 17
“The Teacher Breaks the Cage. The Prison of Wind Torn by Equations”
The underground magic layer.
The “Cage of Sky Law”—an absolute magical restraint that the Wind Nation Elstra prides itself on.
Through interference of wind-attribute spells across hundreds of layers, it erases the coordinates themselves of a target’s magic.
Inside this cage, no spell or magical formula can exist.
And now, at its very center—Lutia von Valenstein was imprisoned.
(Ugh… my power… it’s completely…)
No matter how much magical energy she poured in, nothing happened.
(Does he… know that I’m here…?)
(Please… come. Come, Kai…)
It was then.
A snap—at a corner of the space, a “distortion” appeared.
In an instant, a single white line streaked across the ground.
“…Hoh. So you’ve appeared.”
Zelda Farion smiled.
Wrapped in wind, her robes billowing, she fixed her gaze on that man standing beyond her.
“To come this far in the role of a teacher…”
“A teacher’s job is to go wherever the students are, no matter what.”
Kai Cross held only chalk and a sketchbook in one hand.
“The Cage of Sky Law cannot be broken.
It’s a space where magic can’t even activate.
For someone like you, who doesn’t fight, there’s nothing you can do.”
“Sure seems that way.”
Kai quietly moved his chalk.
On the cobblestones, a complex concentric pattern of equations began to appear.
(x−a)2+(y−b)2=r\sqrt{(x – a)^2 + (y – b)^2} = r sinθ=y/r,cosθ=x/r\sin\theta = y / r, \quad \cos\theta = x / r ∴θ=tan−1(y/x)\therefore \theta = \tan^{-1}(y / x)
The moment the formula activated, the airflow shifted.
“What… this redefinition of… coordinates…!?”
“The theory of the Cage of Sky Law traps you by erasing the initial coordinates of magic.
So, why not just redefine those coordinates?”
“Impossible…!”
Formula magic—a theory- and equation-based “coordinate regeneration” magic.
By making magical energy “exist again” at a new position, it circumvents restraint.
A completely mathematical approach no one in another world had ever attempted.
“I’m not a ‘wizard.’
But I am confident in making things understandable.”
The moment the formula activated—
The space around Lutia collapsed with a sound.
The wind membrane tore apart, and the cage vanished from the newly redefined area.
“…My power… it’s coming back…!”
Kai caught Lutia as she nearly fell to the ground.
“I’m glad you’re safe.”
“…Why… did you come?”
“Because I’m a teacher.”
“Just… that?”
“…Maybe not.”
Kai’s voice was just slightly gentle, just slightly trembling.
But then, the air shifted violently again.
Zelda Farion quietly snapped her fingers.
“Then, it’s our turn.”
Behind him, six magical circles began to rotate.
“Knowledge is indeed strong. But I shall teach you that it is powerless before force.”
The “Wind Split Sixfold Rotational Array”—
Zelda’s signature, as the head of a nation’s mage corps: a combination of wind blade and spatial interference magic.
Yet Kai did not step back.
He opened his sketchbook and began drawing equations parallel to the magic circles.
cosθ+sinθ=2⋅sin(θ+π/4)\cos\theta + \sin\theta = \sqrt{2} \cdot \sin(\theta + \pi/4) ΔE=−∂Φ∂t\Delta E = – \frac{\partial \Phi}{\partial t}
“Mixing physics makes it interesting, doesn’t it?”
“What… this reaction formula…!”
The air pushed back, and the wind blades reversed.
“No way… did he… redefine the magic in the opposite direction!?”
“Exactly. ‘Magic to stop magic’—mathematically, it works, you see?”
The battlefield fell silent.
Zelda stayed quiet for a while, then shrugged and smiled.
“…Interesting. You are indeed a threat. But—”
“Next, the entire nation will move. Be prepared.”
He then retreated, riding the wind.
Silence returned to the magical layer.
Lutia buried her face in Kai’s chest, collapsing from relief.
“Idiot… idiot… why are you like this…!”
“This isn’t the time for crying.”
“I’m not crying… I’m not…!”
But her voice trembled.
Deep down, her heart screamed that she didn’t want to lose him.
◆◇◆
That night.
Kai carried Lutia back to the school.
In an empty auditorium, he whispered softly.
“It’s ridiculous… a math teacher beating magic…”
But in the next moment, a small hand quietly touched his back.
“Kai-sensei… thank you.”
It was Philia.
In the returned girl’s eyes, feelings that couldn’t yet be spoken were clearly alight.
