Chapter 40: The Solution

The next morning, at the Senju Clan's rear mountain.

Yuto sat on a smooth green stone slab, eating rice balls and dried meat that Tsunade brought him, occasionally sipping hot fish soup.

At thirteen, Yuto was at the age when 'a growing boy can eat an adult out of house and home.' As a shinobi, his appetite was enormous. Shizune stared at the empty food box in astonishment, as if seeing a rare animal.

"You... you won't explode like a balloon, will you?" Shizune asked, eyes wide.

"Of course not," Yuto said, patting his stomach. "I'm not foolish. Once I'm full, I stop eating." He paused, puzzled. "Sensei is a taijutsu master. Her appetite should be bigger than mine."

Nearby, Tsunade, who was fixing her hair, shot him a glare. "It's very rude to comment on a lady's appetite, you know."

While they talked, Yuto finished his meal and took a deep breath. "I'm done... Yeah, about seventy percent full, which is perfect for training."

Shizune picked up the food box and, since she had to go to school, didn't dawdle and skipped down the mountain.

Tsunade watched her student leave and sighed. "You're only a year older than Shizune, yet you're much more mature..."

Yuto stood up without replying, distancing himself and stretching his wrists and neck, also removing his bandages.

Tsunade chuckled. "Being cautious, huh? Don't worry, I won't ambush you..." She beckoned to him. "Come on, use that jutsu on me."

"Sensei..." Yuto said seriously. "If I hit you directly, it could be deadly."

"You won't burst from eating rice balls. Do you think I'm foolish enough to take the hit head-on?" Tsunade retreated. "Come on, my cute student. You're a hundred years too early to think you can kill me."

Yuto understood. With her "Strength of a Hundred Seal" allowing her to use "Creation Rebirth," her recovery ability was unparalleled in the ninja world. She could handle it without worry.

Heat rose in the back mountain, the leaves instantly dried and withered, and sweat beaded on Tsunade's neck and face. This was just the prelude, nearly setting the forest ablaze.

'This jutsu's power exceeds my expectations...' Tsunade thought. She didn't hesitate, biting her thumb and slamming her hands on the ground. "Summoning: Rashomon!"

Boom!

A giant gate appeared in the forest, massive and imposing, like a small mountain, with a grotesque face carved on it, making it intimidating.

"Lion's..." Yuto murmured, charging forward. "Fang Bite!"

He struck the middle of the summoned Rashomon, the impact shattering the surrounding trees. With a loud boom, Rashomon was penetrated, the edges melting into molten metal.

Yuto wavered but quickly reached Tsunade, his right hand striking her abdomen.

With the residual force of "Lion's Fang Bite," he knocked Tsunade through over ten trees before finally stopping.

'I overestimated myself. I shouldn't have taken the hit directly,' Tsunade thought bitterly but maintained her composure. "That's enough... Yuto."

The chakra dissipated. Hearing his teacher's words, Yuto quickly withdrew his hand.

Tsunade's clothes were shredded at her abdomen, revealing her fair skin, imprinted with Yuto's handprint.

"Impressive, Yuto." Tsunade examined the damaged Rashomon and her own injuries. "Although the high temperature and fangs are flashy, the real damage comes from the rapid flow of chakra. Unlike the Rasengan's central rotation, your jutsu is more complex, with many small vortices and counter-directional mini-whirlwinds... Ouch."

She winced, touching her bruises. "The internal organs are damaged too... It feels like an earth release blunt force, and the air-splitting charge resembles lightning release... Honestly, after piercing Rashomon, this still has such power. An ordinary Jonin would die from this, and most defensive jutsu would be ineffective."

"It's an excellent jutsu, very suitable for you, but it has flaws."

"Your arm must be hard to lift now. The strain on the user is immense. It's unquestionably S-rank but would also be classified as a forbidden technique."

Tsunade rubbed her abdomen, her fair skin marked by burns and cuts, with bruised internal organs beneath.

As she pondered how to mitigate the jutsu's side effects—Tsunade wasn't a masochist. She had Yuto injure her to better understand the jutsu.

Lion's Fang Bite's self-harm aspect stems from its dual nature of damaging the enemy while similarly affecting the user. The difference is merely in degree, but the destructive principle is identical.

To perfectly address this burden, one must experience the same trauma as the user.

Tsunade's years of combat had ingrained reflexes in her. At the moment Yuto's hand touched her abdomen, she almost instinctively retaliated. She understood that Yuto had a chance to "bite" through her waist.

Yuto... held back at the last moment, Tsunade realized, glancing at him. This student was reliable, understanding the limits.

As she healed her abdominal injury, Tsunade contemplated neutralizing the jutsu's severe side effects.

The best method would be adding a "membrane" between the body and the external chakra, blocking the violent chakra's self-harm. However, this would greatly shorten Lion's Fang Bite's duration, even causing it to collapse instantly, as the protective layer would also obstruct Yuto's chakra.

"Unidirectional fluid transport," Tsunade thought suddenly. It could transmit chakra while blocking destructive force...

To her knowledge, no physical material had this property.

Reluctantly, she considered that a "slug" might suffice. Before using the jutsu, wrapping the slug around the arm could work, as slugs are immune to physical attacks and can transmit chakra as summoned creatures. But this would be too disrespectful to the slug and impractical in the unpredictable conditions of ninja battles.

Tsunade rubbed her forehead, suddenly thinking of her "Strength of a Hundred Seal."

An alternative approach that didn't involve blocking but a more subtle method to mitigate the damage flashed in her mind.

—Sealing!

(End of Chapter)