Naruto: How to Be an Undercover Shinobi

Shikkotsu Forest.

Tsunade stood before the massive Katsuyu and smiled, giving a small wave.

"Katsuyu, it's been a while."

"It has, Lady Tsunade."

Katsuyu's voice was that of a young girl.

After a brief exchange, Tsunade looked up at the mountain-sized Katsuyu and asked politely,

"Katsuyu, is it okay if I bring someone over? A friend!"

Katsuyu nodded.

"Is it Lady Tsunade's boyfriend? Do you need a summoning contract scroll?"

Boyfriend?

Tsunade's face turned bright red. She shook her head furiously, stammering.

"N-no... no, he... he hasn't even confessed yet!"

As she spoke, she quickly covered her flushed face with her hands.

It took her a while to recover. A faint blush still lingered on her smooth cheeks.

"I-I'm starting."

With that, she smoothly formed a sequence of hand seals.

Boar, Dog, Rooster, Monkey, Sheep.

"Summoning Jutsu!"

With a burst of white smoke, Reiji emerged, eyes wide in shock as he looked up at the mountain-like slug.

Holy crap!

This thing is massive!

At the same time, Katsuyu was just as shaken.

It wasn't surprising that Tsunade summoned a person. What startled her was how bizarre this person was. Every cell in his body was constantly absorbing natural energy.

Staring at the stunned Reiji, Katsuyu couldn't help blurting out her thoughts.

"You don't seem like someone who should be walking around on legs!"

"..."

What's that supposed to mean?

You want to bury me in the ground too?

Noticing Reiji's puzzled expression, Katsuyu quickly apologized.

"Sorry, that just slipped out. Please don't mind it."

Seeing the enormous head droop down, Reiji instinctively took a step back and waved his hands.

"No, no, I'm not offended. It's not the first time I've heard something like that."

Katsuyu grew curious.

"Someone else said that?"

"Yeah, both Matatabi and the Nine-Tails said it. They were even harsher. Said I should be buried underground."

Katsuyu froze.

She didn't know exactly what Reiji was, but her instincts told her the comment made sense. Reiji gave her the feeling of someone who shouldn't be roaming around—like he was meant to stay put.

Tsunade watched with interest, secretly wondering what "burying in the ground" could mean.

Wait... when did he talk to the Nine-Tails?!

Realization hit her. Eyes widening, she stared at Reiji in disbelief.

The Nine-Tails was sealed inside Grandma Mito. Don't tell me...

Her face darkened instantly. She stepped forward and grabbed Reiji's ear.

"You—when did you talk to the Nine-Tails?!"

What the hell?!

This woman's ambushing me again?!

Can't you show some mercy to my ears?!

Rolling his eyes, Reiji gave a rough explanation about how he used to be a Jinchūriki.

Only then did Tsunade let go, looking a little embarrassed. She even rubbed his ear gently twice.

"Sorry, I just get nervous thinking about how old Grandma is."

"..."

Reiji was speechless. He instinctively backed away a few steps, distancing himself from this woman with no sense of restraint.

Watching them, Katsuyu chuckled.

"You two get along so well~"

"Hehe~" Reiji gave a small laugh, then steered the conversation back on track.

"Katsuyu-sama, I actually came here to ask about Sage Mode."

At his words, Katsuyu shook her head and replied plainly,

"You don't need to learn Sage Mode. Your cells are already absorbing natural energy every second.

Sage Mode just increases the ratio of natural energy in senjutsu chakra."

Reiji blinked, a bit confused.

My cells are absorbing natural energy?

Why don't I feel anything?

Could that be the secret behind my immortality?

With that thought, Reiji looked up at Katsuyu and spoke earnestly.

"Katsuyu-sama, can you sense how fast my cells are absorbing natural energy?"

"Yes, I can~"

Hearing this, Reiji nodded.

"Then please check if the rate at which my cells absorb natural energy has increased."

As he spoke, Reiji silently activated a technique in his heart.

Lightning Release Chakra Mode, activate!

In an instant, a powerful gust of wind swept out, and blue lightning crackled across his entire body.

Immediately after, Reiji raised his right hand and extended his index finger.

"Hell Stab: One Fingered Assault!"

With a quiet shout, and under Katsuyu and Tsunade's slightly tense gazes, Reiji's right index finger jabbed straight into the palm of his left hand, piercing the skin.

Seeing this, Reiji quickly deactivated Lightning Release Chakra Mode and raised his injured left hand in frustration.

Damn it, if I keep training like this, even One Fingered Assault won't break the skin anymore!

At that point, I'll need to stab a hemorrhoid just to draw blood!

The thought of future battles crossed his mind...

The Sannin simultaneously biting their fingers and shouting: "Summoning Jutsu!"

Katsuyu, Gamabunta, and Manda all appearing in a flash.

Then there'd be him, biting his thumb so hard he chips a tooth, scraping a bit of blood from the gumline with his finger... At that point, Reiji might as well ram his head into a wall.

This is just too damn embarrassing!

Just as Reiji's expression grew gloomier, Katsuyu spoke up.

"The rate at which the wound absorbed natural energy hasn't increased~"

Hearing that, Reiji looked down at his palm—already fully healed—and was dumbfounded.

So, the regeneration of this immortal body has nothing to do with absorbing natural energy?

With that thought, Reiji looked up at Katsuyu.

"Katsuyu-sama, I still want to learn Sage Mode."

Katsuyu paused to think, then nodded.

"Sage Mode is essentially the process of mixing natural energy with your own chakra in a specific ratio to produce 'Senjutsu Chakra'.

It's a state that allows you to utilize natural energy."

"What's the ratio?" Reiji asked curiously.

"I don't know. It's different for everyone."

Hearing that, Reiji nodded and turned toward Tsunade, who was standing nearby.

"Tsuna, why don't you train in Sage Mode?"

At that, Tsunade lifted her chin proudly.

"I don't need it."

What she actually wanted to say was that she was a little scared of the consequences of failure.

According to Katsuyu-sama, those who fail in Sage Mode training turn into trees here in Shikkotsu Forest.

She didn't want to become a tree and spend the rest of her life in this cold, damp place.

Seeing how eager Reiji looked, Tsunade couldn't help but try to talk him out of it.

"Reiji, are you sure you don't want to reconsider?"

"No need." Reiji waved a hand and gave her a reassuring look.

He knew his body better than anyone.

What's the point of being immortal if you can't push your limits?