E=mc^2

"First, before I explain why chakra still obeys the law of conservation of mass and energy, I need to tell you about the relationship between mass and energy."

"E=mc^2. This formula is incredibly famous. It reveals the relationship between mass and energy."

"When I first saw this formula, I was rather dismissive. My thinking back then was incredibly naive. 'The units on both sides of the equals sign are the same. So what? Anyone can do that.'" Chuanhe sounded a little wistful.

"But after I understood what energy was, I stopped thinking that way. Do you remember how I explained energy to you?"

"I compared matter to equipment and energy to its attributes."

"Real matter transforms into energy, which doesn't truly exist. If I had to explain it using a term that most people in this world could understand..."

"That term would be—transformation between the real and the unreal."

His father's words startled Hui. Abstract concepts were certainly hard to grasp, but he understood a lot more as soon as he heard the phrase "transformation between the real and the unreal."

"What makes this formula so fascinating isn't its physical meaning. Instead, it's the destructive power it represents that made it famous."

"Heh. Destruction. How ironic."

"E=mc^2."

"The standard unit of mass is the kilogram."

"Do you know what kind of explosion you'd get if one kilogram of matter were completely converted into energy?"

"About 1,400 Little Boys."

"Each one might have an effective killing radius of just under a kilometer against an elite jonin. But it could level every building across an area the size of Konoha."

"You wouldn't need a whole kilogram. Just one gram could blow all of Konoha sky-high."

"Matter isn't so simple, Hui. The energy inside it is beyond your imagination."

"But releasing that energy is incredibly difficult. This weapon is an ultimate weapon even back where I come from. It can only convert a few thousandths of the matter."

Hui listened to his father in silence. Ever since his father had started teaching him theory, he had gradually begun to realize that perhaps his father wasn't from this village.

Could he be a spy from another hidden village? But Hui didn't care. So what if he was a spy? His father was the only family he had left.

All he needed to do was become strong before all this came to pass—stronger than anyone else. That way, he could protect his father.

But lately, Hui had realized that his father didn't seem to harbor any ill will toward the clan. So he had also begun to take another look at his clansmen.

That was why he had ultimately decided to befriend Sasuke.

"You may have been wondering why I've only taught you shortcuts."

"Because I never intended for you to become a ninja. You were the one who wanted to attend the Ninja Academy, Hui. Since it's your dream, I'll support you all the way."

"Heh. People are always better at destruction than creation. I'm no exception."

"I once dreamed of becoming a ninja as powerful as Uchiha Madara. Things didn't work out that way. By the time I was able to pick that dream back up, I no longer had what it took. My fighting style is completely set now."

Hui was curious. From the sound of it, his father's fighting style was completely different from a ninja's. Which hidden village had someone like that?

"Your life has only just begun, Hui. You have plenty of time to think about what kind of person you want to become and what you want to achieve. Whatever you choose, as long as it doesn't go against my principles, your father will support you."

"I'm getting off track. Sigh, the older you get, the more you worry about."

"Where was I? Oh, right. Before we continue with the next lesson, let me explain two concepts to you."

"Antimatter and negative-mass matter."

"These two things are completely different, Hui. Don't mix them up."

"Antimatter... Do you remember what I told you about atomic theory? Take electrons, for example. The antimatter counterpart of an electron is a positron. It carries an equal amount of positive charge."

"If a positron comes into contact with an electron..."

"Annihilation occurs."

"All of their mass is converted into energy, just as the formula says."

Hui voiced his confusion. "Father, can annihilation only happen between antimatter and matter that correspond exactly?"

Chuanhe replied, "You're right, Hui. Not every kind of antimatter will annihilate as soon as it touches matter. They have to correspond exactly."

"But even I have a lot of questions about that conclusion. Unfortunately, the antimatter I have is extremely scarce, so I haven't been able to conduct that experiment yet."

Hui shuddered. Antimatter? An explosion? Konoha? Was his father planning to destroy the entire village?

Chuanhe naturally noticed what Hui was thinking.

"Don't worry, Hui. Your father is a kind man who can't bear to see people suffer. Heh. I just run away from their suffering. I'm not a terrorist, either. Antimatter is only one of my research topics. In fact, because it's so difficult to produce, it has almost no practical use."

"Maybe once I've fully worked out how chakra without an affinity transforms into elemental chakra with properties similar to physical matter, I'll be able to produce antimatter on a large scale."

"I'm getting off track. Now let me explain negative-mass matter."

"Just as the name suggests, it's matter with negative mass. It's deeply counterintuitive."

"Ordinary matter falls toward the ground because of gravity. Negative-mass matter, on the other hand, would fly up into the sky because of its properties."

Hui once again felt as if his brain couldn't keep up. He could understand antimatter to some extent. But what was negative mass? Could such a bizarre thing really exist?

Looking at Hui's scrunched-up face, Chuanhe said, "I confirmed it existed based on a conclusion I remembered. I recall that an experiment proved the existence of negative energy. So, according to this mass-energy equation, doesn't that prove negative mass exists too?"

(Note: No such relationship exists in the real world. This is Chuanhe's misunderstanding.)

"Do you have any questions now, Hui?"

"Father, based on what you said, would negative-mass matter annihilate if it came into contact with positive-mass matter?" Hui voiced his confusion.

"Well, how should I put it? Probably not. But we'd need an experiment to confirm that. Unfortunately, I haven't obtained any negative-mass matter."

"Antimatter is antimatter, and negative mass is negative mass. They're different; they aren't the same thing. Even antimatter still falls normally under gravity. That's what makes them different."

Hui nodded to show he understood.

"Well, Hui, we've finished all the preliminary preparations. This was supposed to be the subject of the third lesson, but since you've already understood this much, we might as well carry on."

As he spoke, Chuanhe stood up and looked around. Then he closed his eyes, formed Hand Seals, and performed a jutsu Hui didn't recognize.

Hui felt an invisible wave of chakra spread rapidly outward from his father.

Judging by the looks of it, this must be a Sensory Ninjutsu, Hui thought.