The three of them did not head toward the training ground.
Shin-chan followed Namikaze Minato through two streets and finally stopped in front of an old apartment building.
"We're here." Namikaze Minato took a key from his pocket.
Shin-chan looked up at the doorplate. "Where is this?"
"My home." Namikaze Minato pushed the door open and stepped aside to let Shin-chan go in first.
Shin-chan stood at the entrance, tilted his head, and peeked inside.
"It's so small."
Namikaze Minato placed the key on the low table. "For one person, it's enough."
"Aren't we going to the training ground?"
"We have to learn some theory first." Namikaze Minato took a pair of small slippers from the shoe cabinet and placed them at Shin-chan's feet.
Shin-chan stuffed his feet into the slippers. They were a little too big, making a slapping sound as he walked.
Kushina was the last to enter. She naturally walked into the kitchen and opened the small cabinet above to take a look.
"Minato, you don't even have tea leaves here."
Namikaze Minato looked back. "I don't usually drink tea."
"What if guests come?"
"You're not a guest."
Kushina's hand paused for a moment. Then she closed the cabinet door, the corners of her mouth lifting just a tiny bit.
Namikaze Minato picked up a scroll from the table and spread it out in front of Shin-chan.
The scroll was covered in dense jutsu formulas. Some parts were drawn like concentric circles, spreading layer by layer from the center.
Shin-chan stared at it for three seconds.
"Is this a maze?"
Namikaze Minato's finger landed at the center of the formula.
"This is the structural diagram of the Flying Thunder God Technique's formula."
Shin-chan leaned in a little closer.
Minato's fingertip slowly moved outward from the center. "The core of the Flying Thunder God Technique is using a formula to mark and sense spatial coordinates."
Shin-chan stared at Namikaze Minato's face for several seconds. "I completely don't understand."
Namikaze Minato smiled and traced a circle around the outermost ring of the formula.
"Let's put it this way. Imagine this."
Shin-chan placed both hands on his knees and looked at him very seriously.
"You have a toy box at home," Namikaze Minato said. "And you put a sticker on that toy box."
"But my toy box doesn't have room for any more stickers."
"Then imagine you have a new toy box." Namikaze Minato tapped the center of the formula. "You put a sticker on that box that only you can touch."
Shin-chan's expression became serious.
"Then no matter where you go, as long as you close your eyes and think of that sticker..." Namikaze Minato lifted his hand from the scroll. "You can return to that box in an instant."
"Then if I put the sticker on Mom, I won't have to walk home after school?" Shin-chan's mouth opened wide.
Namikaze Minato froze for a moment, then laughed. "More or less, but it can go much farther than that."
"How far?"
"As long as the formula remains, no matter where you are, you can instantly return beside the mark."
"Then I want to learn it!"
Namikaze Minato pushed the scroll forward.
"But this technique is very difficult."
Shin-chan's enthusiasm was blocked by those words. He tilted his head and waited for him to continue.
"The formula is your sticker." Namikaze Minato tapped the scroll. "These patterns are the Flying Thunder God's sticker."
Shin-chan brought his face close to the scroll.
"These patterns look really hard to draw."
"They are very hard." Namikaze Minato said, "That's why the Flying Thunder God Technique is called an S-rank ninjutsu."
Shin-chan looked up at him.
"Can you draw it?"
"I can draw part of it, but it still isn't complete enough." Namikaze Minato shook his head. "For the Flying Thunder God formula to be stable, you have to understand the basic principles of sealing techniques. Otherwise, the patterns you draw are just a bunch of lines, unable to carry chakra."
Shin-chan's expression went from confused to even more confused.
"What are sealing techniques?"
Namikaze Minato thought for a moment.
"It means locking things away," he said. "For example, locking chakra in a fixed position so it can't escape."
Shin-chan blinked.
"Like locking green peppers inside the refrigerator?"
Namikaze Minato smiled. "More or less."
Shin-chan's expression immediately turned solemn.
"Then that's very useful."
Namikaze Minato turned his head and glanced toward the kitchen.
"When it comes to sealing techniques, Kushina knows much more than I do."
Shin-chan followed his gaze.
Kushina was leaning against the kitchen doorway, arms crossed in front of her chest, with a meaningful smile on her face.
She had been waiting for this moment for a while.
"Big Sister here possesses a wealth of knowledge about sealing techniques," Kushina said slowly as she walked over and crouched in front of Shin-chan.
Shin-chan looked at her.
"In all of Konoha, when it comes to sealing techniques, there aren't many who know more than me." Kushina's tone carried obvious pride.
Namikaze Minato coughed lightly beside her.
"What?" Kushina looked at him.
"Nothing." Namikaze Minato's gaze drifted toward the ceiling.
Kushina turned her attention back to Shin-chan, the corner of her mouth curving upward.
"Well? Want to learn?"
Shin-chan nodded.
"Then." Kushina brought her face a little closer. "As long as you say, 'Pretty big sister, please teach me sealing techniques,' I'll teach you the basics of sealing techniques. How about that?"
Shin-chan and Kushina looked at each other for about two seconds.
Then Shin-chan tilted his head to one side and looked her up and down.
"But you're not a big sister."
Kushina's smile froze on her face.
"What did you say?"
"A big sister has to be at least eighteen." Shin-chan held out both hands and counted on his fingers. "You're still a child."
Kushina's expression stiffened.
Namikaze Minato silently turned his head toward the window.
Then Kushina's hands reached over, pinched both of Shin-chan's cheeks, and pulled them to the sides.
"You—little—brat—"
Shin-chan's mouth was stretched into a flat shape, and his muffled voice leaked out.
"But I'm telling the truth."
"Even the truth isn't allowed!"
"Then are you going to teach me sealing techniques or not?"
Kushina let go, and Shin-chan's cheeks snapped back to normal.
She stared at Shin-chan for a few seconds, then suddenly smiled.
"I'll teach you," she said. "But you owe me one 'pretty big sister.' Whenever you finally think I look like one, you'll pay it back."
Shin-chan rubbed his cheeks and nodded seriously.
"Okay."
Namikaze Minato quietly breathed a sigh of relief from the side.
Kushina sat cross-legged on the floor and spread a sheet of white paper in front of Shin-chan.
"The essence of sealing techniques is locking chakra away." She picked up a pen and drew a circle on the paper. "For example, an enemy's chakra, or even an enemy's movement, can be sealed."
Shin-chan crouched in front of the paper, propping up his face with both hands.
"Look at this." Kushina drew several symbols inside the circle. "This is the simplest sealing formula structure. The outer circle is the boundary, and the symbols inside are the lock."
Shin-chan leaned closer.
"What happens after it gets locked?"
"A sealing formula appears on the sealed person's body." Kushina tapped the paper with her finger. "Then their chakra won't be able to move."