Chapter 25
“Mathematical Swordsmanship Training! The Secrets of Patterns and Angles”
Academy Event Arc: Battle Ridge Festival II
Only one week remained before the Battle Ridge Festival.
Kai’s class, gathered at one corner of the schoolyard, stood stiffly with swords in hand.
“Teacher… can we really win using swords?”
“Yeah, we’re good at magic and all, but we’ve never even held a sword before…”
Hearing their anxious voices, Kai grinned.
“Don’t worry. Swordsmanship’s all about patterns and angles. In other words—trigonometry and mechanics.”
“…Trigonometry?”
“Mechanics?”
Kai picked up a wooden stick and drew a triangle on the ground.
“For example, take a thrust. If you swing down at a 30-degree angle, you can slip past your opponent’s defense with maximum efficiency.”
“Wait—30 degrees!? Where’d that number come from!?”
“sin 30° equals one-half. Meaning—‘maximum effect with half the effort.’”
“…W-what does that even mean?”
“You’ll get it after doing it a hundred times.”
Without further explanation, Kai handed a wooden sword to one of the students and had them thrust at a target.
At first, the student swung down with brute force—the target only wobbled.
Kai placed his hand over the student’s arm and adjusted the angle.
“See? 30 degrees. Keep your center of gravity in your hips, vector forward.”
ZBAAAN!
The wooden target split clean in two.
“N-no way…!”
“It’s true! I barely swung that time!”
“Next, slashing. Think of your arm’s motion as an arc. Remember the Inscribed Angle Theorem?”
“The… inscribed angle…?”
“When the angle stays constant, the result’s the same no matter where you strike from.”
Kai demonstrated.
He gave a light horizontal swing—SWISH! The bundle of straw sliced cleanly in half.
“It’s not about power. It’s about controlling the trajectory.”
Lutia stepped forward.
“Hmph. I don’t need this kind of training. I’m already strong.”
Kai smiled wryly and adjusted her stance.
“You’re twisting your wrist too much. Not 90 degrees—make it 75. Shift your weight half a step back.”
“There’s no way such a tiny change would—”
SWAAN!
Her strike cut through two targets at once.
The entire class burst into applause.
“…! T-that was just because I’m strong!”
“Sure, sure. Got it—classic tsundere angle, 45 degrees.”
“Who’s a tsundere!?”
The next day, Kai drew a circle in the sand and had the students stand around it.
“This is vector training. You’re learning how to release the reaction force after a sword swing.”
“Reaction force…? Like, physics?”
“Exactly. Swordsmanship is an exchange of forces. F = ma. Mass times acceleration.”
“Sensei! There are equations flying around while we’re fighting!”
“Equations are the strongest weapon of all!”
Though confused at first, the students quickly improved with repetition.
“Sensei! I can cut faster than yesterday!”
“My thrust slipped right through the opponent’s guard!”
“I’m not scared of the sword’s recoil anymore!”
Their eyes shone with excitement; laughter filled the yard.
Then, watching from the sidelines, came Lutia’s older brother Wilhelm and Julius.
“Sister, you’re training with swords?”
“And under Lord Cross, no less.”
The two crossed their arms and watched intently.
“…Unbelievable. A class focused on magic can move like this?”
“Their patterns are precise. No wasted motion. Entirely logical…”
“Heh. See? I was already strong, but Sensei just refined me even further.”
“Yeah, sure—you were flailing around at first.”
“Silence!”
By the time training ended, the students were drenched in sweat and covered in sand—but smiling brightly.
“Sensei, do you think we can win the Battle Ridge Festival?”
“I don’t know if you’ll win. But I do know you’ve built the form of victory. The rest… is up to you.”
The once-gloomy mood cleared instantly.
Lutia crossed her arms and nodded firmly.
“Then I’ll prove it with a sword. The Cross Class is the strongest there is!”
And so, the mathematically-backed swordsmanship training advanced smoothly—
setting the stage for the Cross Class’s abnormal strength to be revealed in the coming battle.
