In another world, Lu Mingfei is learning card making.

"Huh—how did you finish it?"

Rong En flipped through the mental arithmetic worksheets, his face showing undisguised surprise: "You can finish it in one class period? I dare say, even the older students couldn't do that..."

"They couldn't even do it?" Lu Mingfei blinked. "Then what did they learn in those extra two years of arithmetic class?"

"No, arithmetic is only taught in the first and second grades. It stops in the third grade." Rong En closed the mental arithmetic flashcards and put them back on Lu Mingfei's desk. "The second-grade math class... I heard my sister mention it. They talk about things like Abel groups."

"Huh?" Lu Mingfei blinked. It was a new term for him, but considering that first graders learn addition, subtraction, multiplication, and division, this second-grade stuff probably wouldn't be too difficult...

"Let's not talk about that, Lu Mingfei." Rong En grabbed Lu Mingfei's shoulder. "How did you do that so fast? Can you teach me?"

"Of course," Lu Mingfei blinked. Since Rong En could teach him the family's wand combat technique, it wouldn't be a problem for him to teach him a basic vertical spell learned in elementary school.

Anyway, Rong En is already thirteen years old. No matter what, learning a vertical calculation that an eight or nine-year-old child can learn... shouldn't be a problem, right?

Lu Mingfei thought about the curriculum of St. Marian College and suddenly had some doubts—St. Marian College spends the whole year learning addition, subtraction, multiplication and division, so there must be a reason for this curriculum.

So what's the rationale behind this arrangement?

……

"Ah, great Marianne, I shouldn't have doubted your course arrangements." Lu Mingfei covered his eyes, not wanting to look at Rong En next to him.

In the past half hour, Lu Mingfei had a very good plan: first, he would explain Arabic numerals to him, then the multiplication table, and finally break down each step of the vertical calculation and teach him. In this way, Rong En would master the four arithmetic operations, and half an hour would be enough to finish half a year of teaching at St. Mary's.

But reality dealt him a heavy blow:

"You say, one is simply one, so why can a single vertical stick represent one? And why does two have to be so convoluted? If we put two 'ones' together, can't we represent two?"

"Two ones together equal eleven? Why represent it that way? I think two ones together represent two, which is fine. Can't we make it represent two instead of eleven?"

"Get out!" When Rong En said, "We can represent the higher digits vertically, like 'twenty-four,' we can draw two vertical bars on top and four vertical bars below," Lu Mingfei finally couldn't suppress his anger and swore for the first time.

Lu Mingfei had never imagined that teaching a simple vertical calculation could be so complicated. He suddenly felt a little sorry for the teachers he had met on Earth.

Keep in mind, he only needs to teach one person, while his elementary school teachers taught several classes, totaling hundreds of students...

Thinking of this, Lu Mingfei simply lay down on the table. Rong En quieted down after being yelled at—of course, it was also possible that Professor Sarah Venus had unusually 'floated' in, unfolding her translucent wings, a symbol of fairies, behind her.

"Let's begin the lesson." Professor Sarah raised her hand and pointed, and the chalk floated up and began to write on the blackboard.

……

After class, Rong En hesitated and slowly moved towards Lu Mingfei. Lu Mingfei looked at him and sighed again:

"You still want to learn, right?"

"Yes." Rong En immediately raised a hand, pointed to the sky, and swore, "I promise I won't act on my own and will completely follow your teachings!"

"Teacher, please teach me that magical spell that lets me finish an entire workbook in thirty minutes!"

"That thing isn't magic..." Lu Mingfei rubbed his forehead and sighed. "Let's go eat first, and I'll teach you when we get back to the lounge."

In the dining hall and lounge, Lu Mingfei and Rong En walked side by side. On the only path leading to the Knights' Academy tower, as they passed through layers of curtains, Rong En suddenly grabbed Lu Mingfei's arm:

"Someone is following us."

The two continued walking forward, communicating in hushed tones:

Lu Mingfei: "Who is it?"

Rong En: "Not sure, but judging from his build, he should be a freshman or a second-year student. Is he being followed because of your identity as the Hero's Son? Has anyone been sending you information?"

Lu Mingfei: "No one passed on any intelligence, so it shouldn't be because of my identity."

Rong En: "Should we subdue him first?"

Lu Mingfei: "Okay."

Behind the second curtain, the two stopped simultaneously and pulled out sticks. The curtain rustled, and a brown-haired girl emerged from within—

She was immediately pushed to the ground by the two men, who crossed two sticks behind her back to hold her firmly in place.

"Tell me! Why are you following us?" Rong En asked first, while controlling his stick to roll behind her, crushing her arm bone.

"Ah—I'll talk, I'll talk—" The thirteen-year-old girl couldn't withstand this kind of interrogation, which was practically torture, and almost immediately decided to surrender. "I, I'm a freshman at the Knights Academy. I heard you talking about 'methods to quickly finish the workbook' in the classroom, so I thought I'd follow you and find an opportunity to learn it..."

"Stealing techniques?" Rong En lowered the stick slightly, but his tone remained stern.

"No—it wasn't about stealing my skills, it wasn't about stealing my skills. I wanted to learn openly and honestly, but when I heard you say you were going back to the lounge, I thought I'd follow you and immediately ask if I could learn this method..."

It turned out to be a misunderstanding!

Lu Mingfei understood and prepared to put the stick away when he suddenly noticed Rong En winking at him, gesturing to the new recruits under their command. Lu Mingfei pondered for a moment and then spoke:

"Look, Ron, you're so nervous. I told you there wouldn't be any danger at St. Mary's Academy."

As he spoke, he took the stick away first. Rong En pressed down on the girl's arm with a little more force before putting the stick away.

"Rong En, you went too far!" Lu Mingfei 'questioned' Rong En while showing concern for the girl, and only after sending her back to her dormitory did he walk with Rong En again.

"So you just wanted to learn arithmetic. I thought you were some kind of demon remnant who wanted to kill you at St. Mary's Academy before you grew up." Rong En watched her walk up the stairs before continuing to speak.

"I was startled when I heard someone was following me... Rong En, what were you thinking? Why did you insist on making me put on this show with you?" Lu Mingfei handed the stick back to Rong En and asked.

"I learned this from my dad. He was in charge of training new recruits when he was in the army," Rong En said, recalling the past. "New recruits come in all shapes and sizes. If you train them too hard, they'll cause trouble; if you don't train them hard enough, it won't be effective."

"So my father and his deputy started working together. He was responsible for training the new recruits to the point of exhaustion, while his deputy was responsible for mentoring them and making them see him as a source of support."

"In this way, not only are more and more new recruits becoming successful, but management is also much easier. This method was even praised in public by a general, and it can be said to be my family's 'secret technique'."