Originally, Mito had planned to let Kyuushin and Kushina adapt to life in Konoha for a while before beginning their training in sealing jutsu. However, she was surprised by their eagerness to learn. In that case, it was best to strike while the iron was hot and lay a solid foundation while their enthusiasm was high.
After dinner that day, Mito officially began their instruction. Sealing jutsu, or *Fuinjutsu*, is a type of ninjutsu distinctly different from conventional elemental techniques. It is not known for its destructive power but for its ability to seal an enemy's chakra, body, spirit, or even soul. At higher levels, it can even interfere with space and time, making its applications incredibly broad. The execution of these techniques varies; some, like the Fire Sealing Method and the Five Elements Seal, can be performed by an individual, while others, like the Four Violet Flames Formation, require multiple people working together.[1][7][9]
Because Kyuushin and Kushina were still young and their chakra control was not yet fully developed, their initial lessons focused on the fundamental principles of sealing jutsu.
"Once you have a solid foundation and thoroughly understand the principles, you can seal whatever you wish," Mito instructed them. "If you want to seal fire, use the Fire Sealing Method. If you want to seal lightning, use the Lightning Sealing Method. The subtlety of its application lies in your own understanding."
Kyuushin's eyes lit up. He had previously thought that sealing jutsu consisted only of the few techniques shown in the original work, but he now realized it was far more complex. "So, can you directly seal an enemy's chakra, preventing them from using ninjutsu?" he asked.
"Of course," Mito nodded. "Experience it for yourself." With that, without even forming a hand seal, she placed her hand on Kyuushin. He felt no immediate change; his chakra extraction felt normal. But when he tried to perform the Clone Jutsu, he found that the chakra, which should have flowed freely, was firmly locked inside his body.
"I've sealed all the pathways through which chakra can enter and exit your body, directly sealing your ability to use ninjutsu," Mito explained. "Of course, there is more than one method." She then placed her hand on Kushina. When Kushina tried to extract her chakra, she found it much more difficult than usual, and any chakra she managed to draw was completely uncontrollable.
"You can even do this," Mito said. This time, she formed a few hand seals before placing her hand on Kyuushin. The next second, he collapsed, unable to even control his own body.
Seeing that they had both witnessed true sealing jutsu, Mito chuckled and unsealed them.
"That's amazing, Grandma Mito! I want to learn this!" Kushina exclaimed, her excitement palpable. "Then, if I don't like someone, I'll just seal their chakra and beat them up."
Kyuushin, however, fell into deep thought. He looked at the smiling Mito and asked, "This kind of sealing jutsu must have significant flaws, right?"
"Oh? Tell me."
"First, you have to make physical contact with the enemy to activate it. Second, the duration must not be very long. A large burst of chakra should be able to break the seal."
"Very good, very good. You not only see the surface but also discern the flaws within. One could say you've already stepped over the threshold of sealing jutsu," Mito said, looking at him with approval. "You must remember, although sealing jutsu is versatile, every technique has its flaws. This is true for all ninjutsu."
"What if the sealing jutsu could absorb the enemy's chakra? Wouldn't that eliminate the flaw?" Kyuushin continued to ponder.
"Of course," Mito nodded, then shook her head. "But you must understand that such a jutsu would be incredibly complex. Even I couldn't perform it with a simple touch. In fact, the technique you're describing already exists and is often used on enemy captives."
"But if the captive stops using chakra, and the seal doesn't get replenished, will it dissipate on its own?"
"No, it won't. Even if a ninja doesn't actively gather chakra, there is always some present in the body, which is enough to maintain the seal," Mito explained.
For the rest of the evening, Mito taught them the various basic principles of sealing jutsu, and they benefited greatly. Unconsciously, the night had grown late. Mito felt a sense of unfulfillment, mainly because Kyuushin not only grasped her meaning quickly but also extrapolated from it, causing her to speak more than she intended. She hadn't felt this way in a long time. Her own grandchildren, Tsunade and Nawaki, had little talent for sealing jutsu; they struggled to learn, and she struggled to teach.
As for Kyuushin, though his practical skills were yet to be seen, his comprehension alone was enough to surprise her. Kushina, while a bit behind, was still able to follow along.
"Alright, it's getting late. Let's stop here for tonight," Mito said. Kushina stretched, feeling very sleepy. Kyuushin, however, looked hesitant, as if he wanted to say something but didn't dare.
"Just say what's on your mind. There's no need to be hesitant," Mito said with a smile.
"I want to learn some regular ninjutsu. I wonder if I can?"
"Why do you have that idea? Is sealing jutsu not good enough?" Mito raised an eyebrow.
"Sealing jutsu is very powerful, but I feel it lacks direct offensive capabilities and leans more towards support." Fearing he had offended her, he quickly added, "I want to become a great ninja like the First Hokage, so I want to be more well-rounded."
Mito nodded. Sealing jutsu did have that flaw, but she still put on a serious face. "Every once in a while, I will check your progress in sealing jutsu. If you satisfy me, then learning other ninjutsu is not impossible. However, sealing jutsu must remain your priority, understood?"
Kyuushin quickly nodded. He had no intention of abandoning sealing jutsu, but focusing solely on it would be a waste of his enormous chakra reserves. Moreover, with the cheat of the genetic lock, he wasn't afraid of learning too many things, only of not being comprehensive enough.
"Then, Grandma Mito, please rest early. Kushina and I will head back now."
"These two children..." Mito watched them leave, a smile never fading from her face. At the same time, she thought of her other two grandchildren.
Back in their room, although they were mentally and physically exhausted, their evening practice still needed to be completed. Without accumulating small steps, one cannot travel a thousand miles. If he had mastered the Three Basic Jutsu today, the fight with that genin might not have been so difficult, and he might not have been forced to activate the genetic lock.
*I still haven't worked hard enough,* Kyuushin thought before falling asleep.