Kakashi Masters All Elements, Rewrites the Ninja World for Rin!

In the cave, Kakashi was focused intently, examining Rin's heart with surgical precision.

The deeper he probed, the darker his expression became.

Because what he found wasn't just a regular seal. No, this thing was sinister.

A strange, pitch-black chakra formation bound her heart like a vice. When Kakashi's chakra touched it, it felt like gazing into the abyss—and having it wink back.

"Oh great," Kakashi muttered to himself, "because normal death traps just aren't fashionable anymore."

If he wasn't mistaken—and let's face it, he usually wasn't—this was a hybrid Yin-Yang Seal, the kind that only someone with Six Paths-level hacks could create or dismantle.

Which meant…

Madara. Or worse—Black Zetsu.

"This isn't a seal. This is a death sentence with calligraphy," he thought grimly.

It was a trap. A beautifully disgusting one.

All just to manipulate Obito?

"Kami, Madara, you just love your soap opera plots, don't you?"

His chakra fluctuated slightly with irritation. He wasn't angry often. But this? This crossed the line.

"Fox, are you okay?"

Rin's worried voice interrupted his thoughts. Despite the tension, her concern was genuine.

Kakashi blinked. "Huh? Oh. Yeah, just great. Nothing like discovering ancient god-tier curses before lunch."

"But Ah—Rin, the seal on your heart isn't something I can just peel off like a bandage. I'll have to break it by force. So... brace yourself."

He looked her dead in the eyes.

"If we don't do this soon, things are going to get very bad, very fast."

Rin nodded without hesitation. Her trust in Kakashi was absolute.

"Okay. I'll listen to you."

"Right. Then here's the plan: I'm going to Chidori your heart."

"Wait—what?!"

"You're going to activate Mitotic Regeneration the moment I pierce through it. Heal the wound as fast as possible. If we're even a second off, you die, I scream, Katsuyu panics, and everything goes kaboom."

Rin paled but nodded.

Kakashi didn't waste time. He summoned Katsuyu with a quick flash of chakra.

"Lady Katsuyu, I need your help—Rin will need healing support the moment I hit her."

"Understood, Master Kakashi. I'll assist."

Katsuyu, calm and composed as always, responded gently. She knew Rin well. After all, Rin had signed a summoning contract with her too.

"Thanks," Kakashi said sincerely. "Let's try not to kill my friend today. That'd really ruin the mood."

Now theoretically, if Rin triggered Mitotic Regeneration in time, her heart would begin healing the instant it was pierced. But if not...

Well. Let's not even go there.

Ideally, she would've mastered the Byakugō no Jutsu already. That would've made this safer.

But Kakashi knew better than to rely on ideal.

Even with her absurd talent—and the fact that she was from a civilian family—Rin was pushing the limits already by mastering both Mitotic Regeneration and the Hundred Healings Seal.

She simply didn't have enough chakra control to fully unlock the latter just yet.

If this were a peaceful world, Kakashi would have dragged her back to Konoha, begged Tsunade to take over, and waited until Rin was fully capable.

But this wasn't that world.

He couldn't wait.

The seal was a ticking bomb. And Madara was the lunatic who'd set the timer.

"Don't worry, Master Kakashi," Katsuyu reassured. "I'll do everything I can."

"I'm counting on it."

Kakashi then turned to Rin and... coughed awkwardly.

"So, um... about the next step."

"What is it?" Rin tilted her head.

"I need you to take off your shirt."

"...Eh?!"

Kakashi raised his hands. "Look, it's not me being weird. I mean, I am weird, but this is strictly business. Your shirt might block your reaction timing. And I don't want to miss the heart. That would suck."

Rin flushed crimson.

Still, she looked into Kakashi's eyes—and saw the absolute seriousness there.

"Okay... I trust you."

She began to unbutton her shirt with trembling fingers.

"Wait!"

Kakashi stopped her, walked over to the mouth of the cave, and quickly slammed his hands to the ground.

"Earth Style – Earth Wall!"

A thick stone wall erupted from the floor, sealing off the entrance. For some reason, he shaped it with dog-head carvings.

Because if you're going to block the entrance, you might as well do it in style.

Outside, Shisui tilted his head at the sound, turned, and saw the earthen wall.

He was impressed.

"As expected of Kakashi-senpai. Even his barriers have personality."

He didn't realize the wall was to keep him from walking in at the worst possible time.

Nothing personal.

Just imagine the awkwardness if he barged in while Kakashi's arm was literally inside Rin's chest.

Back inside, Kakashi turned and clapped his hands. "Alright, wardrobe malfunction averted. Let's do this."

"Hmph~" Rin pouted and rolled her eyes, but proceeded to undress behind him.

Kakashi suddenly felt the temperature rise several degrees.

He coughed. "No distractions. Think sad thoughts. Think about Gai's fashion sense. Yeah, that'll kill the mood."

He shook his head violently to clear it.

"Rin, ready?"

"Yes."

"Chidori."

With a crackle, lightning flared in Kakashi's right hand. The signature chirping of birds echoed sharply.

But he didn't strike immediately.

Instead, he compressed the Lightning Chakra further, forcing it to wrap tightly around his arm, until not even a flicker escaped.

So dense was the chakra that even the thousand birds' chirping began to fall silent.

"Huh," Kakashi muttered. "If I compress this any further, I might just invent a stealth Chidori. Call it... Chidori Blackout? No, too dramatic. Maybe... Quiet Murder? Eh, work on that later."

He focused.

"Rin, this is going to hurt like hell. Brace yourself."

"Do it!"

She clenched her fists, eyes shut tight.

Now!

Sizzle!

The Chidori pierced through Rin's chest with surgical precision, and at the exact moment, her seal glowed.

"Ninja Art: Mitotic Regeneration!"

The blue-purple diamond mark on her forehead bloomed and black markings spread, covering her skin.

Simultaneously, her wound began to regenerate.

Kakashi pulled out instantly, blood spraying over his chest.

"Katsuyu, now!"

"Right away!"

Katsuyu surged forward, latching onto Rin's back, while Kakashi cast Healing Jutsu over her chest.

Within a minute, the wound was completely closed.

"Good as new," Kakashi muttered, wiping sweat from his brow.

He looked at Rin and nodded, then turned away.

"You should change clothes. That shirt's looking very... horror-movie."

"Mm."

Rin's cheeks burned as she nodded, pulling out clean clothes from her sealing scroll.

Three minutes later, she was dressed and calm.

"You should change too. You're covered in my blood."

"Sure thing. Just don't peek."

"I won't!"

She quickly covered her eyes with both hands... though Kakashi noticed the slight gap between her fingers.

He chuckled to himself.

"Well played."