Naruto: Unifying the Ninja World, Invaded by Naruto’s Team

"Hm? The top rank is Uchiha Sasuke? The one who fought Naruto's little brother earlier? That doesn't seem right. Why's the seventh rank also this name? And what do 'Original' and 'World Number 1' in parentheses mean?" Kaido asked, eyes wide and confused.

King was equally puzzled.

"My name is Namikaze Naruto, my little brother is Uzumaki Naruto, and the one who just fought Uzumaki Naruto is the Sasuke ranked seventh." Imperial Naruto explained. "'World Number 1' and 'Original' distinguish different worlds. Kaido, since you can come to my world, others from different worlds can too. 'World Number 1' refers to another parallel world similar to ours. Clear enough?"

"Ugh… not really." Kaido scratched his head, baffled.

Seeing this, Imperial Naruto patiently explained further, and after fifteen minutes, Kaido and King finally showed understanding.

"Got it. But Naruto, you're amazing—ranked second in the whole world! So your top-five claim earlier was humble." Kaido praised.

"Second? Not necessarily. Might Guy at third and the Sage of the Six Paths at fourth—we beat each other often. As for Sasuke at first, that's just because he duels more. I wouldn't call myself the second strongest." Imperial Naruto shook his head.

"Is that so? Still, you're top four. Why say fifth?"

"His Majesty is the strongest, no doubt. This ranking excludes him. Everyone's rank starts from second." Imperial Naruto clarified.

"I see." Kaido fully understood.

He scanned further but didn't find Hatake Haruki or Shishui in the top hundred!

(Those kids, though impressive, are nothing special in the Empire. Too many strong fighters here!)

(I can't lag behind! I must get stronger.)

A sense of unprecedented crisis and an urgent desire to grow stronger surged in Kaido's heart.

"Naruto, I want to start training with you right away!" he said seriously.

"Of course. I planned to guide your training. We're passing through here anyway." Imperial Naruto laughed.

◆━⊰✧⊱━◆

The group left the underground training area, arriving at another open space.

There, a man with a ponytail was teaching children.

Imperial Naruto led Kaido and King to him. "Iruka-sensei, this is Kaido, and this is King, guests from another world. I'd like you to teach them the basics of chakra and martial arts training."

"Leave it to me, Naruto-sama!" Iruka Kekaisaran patted his chest.

He then turned to the towering Kaido and King, extending his hand. "You two, I look forward to working with you."

"Iruka… Sensei, right? Likewise." Kaido grinned, extending his massive hand.

◆━⊰✧⊱━◆

One month later, on a barren outskirts of the Empire's city, a loud roar echoed:

"Fire Release: Majestic Flame Annihilation!"

King, clad in black armor with a single helmet opening, spewed fire from his mouth. Flames on his back blazed, enveloping him.

A terrifying fire wave scorched kilometers ahead, baking the ground into a glassy crystal layer.

After this ninjutsu, King shouted again:

"Water Release: Water Dragon Jutsu!"

A dozens-meter-long water dragon rose from the ground.

"Lightning Release: Thunder Beast Battle!"

King's body erupted with lightning, transforming into dozens of roaring thunder tigers rampaging across the ground.

"Not done yet! Earth Release: Earth Wall Turnover!"

The ground rumbled, earthen walls protruding from the earth.

Only then did King exhale slowly, showing a satisfied smile.

*👏🏻👏🏻👏🏻👏🏻*

Clapping sounded beside him.

Iruka Kekaisaran's gentle voice followed. "Well done, King. You're a genius. In just one month, you've fully mastered the chakra system. I'm proud of you."

"Worororo… Iruka-sensei, don't rush to praise King! Now it's my turn!"

"Fire Release: Great Dragon Flame Jutsu!"

A hundred-meter blue-scaled giant dragon opened its mouth, blazing flames erupting. A dozens-meter-wide fire dragon head shot out, expanding to a hundred meters upon hitting the ground, creating vast glass craters.

"Lightning Release: Kirin!"

The blue-scaled dragon roared again, its body spinning, radiating lightning, transforming into a over-200-meter-wide thunder beast crashing down.

"And finally… Dragon Rasengan!"

Chaotic energy gathered, forming a large orb laced with layered black lightning, spewing from his mouth, landing a hundred kilometers away.

*ROAR!*

A deafening rumble sounded.

A massive mushroom cloud soared tens of kilometers high, everything within dozens of kilometers obliterated.

As the smoke cleared, a terrifying crater hundreds of meters deep and kilometers wide appeared.

"Worororo…" Seeing the crater, the blue dragon in the sky laughed heartily.

"Truly remarkable, Kaido. You and King are geniuses among geniuses. Even in the Empire, you'd rank high. But testing new techniques near the city causes too much damage. Don't do this again." Iruka Kekaisaran praised, eyeing the massive crater with resignation.

"Worororo… In the underground metal rooms, it's hard to gauge strength growth! Only outside, in wide areas, can King and I truly feel our changes. Sorry, Iruka-sensei, Naruto-sensei." Kaido's giant dragon form descended, transforming back to human, laughing.

Already strong with fire elemental abilities, Kaido and King learned chakra ninjutsu and martial arts quickly.

In one month, they joined tiered battles, achieving excellent results.

For instance, Kaido entered the top hundred.

With enough time, Imperial Naruto believed he could reach the top thirty.

Kaido was very satisfied with this assessment.

King's strength was around the top hundred, surpassing Haruki and Shishui.

Their training speed showed Empire leaders the potential of pirate world humans.

"Kaido, King, you've passed. You can return to your world now!" Imperial Naruto said, smiling proudly, patting their backs.

"Return? I'm reluctant to part with Naruto-sensei and Iruka-sensei. The thrill of getting stronger is addictive. I haven't felt this in over a decade." Kaido said.

"Hahaha… Martial arts and ninjutsu training never end. Kaido, King, after returning, train more, and you'll grow stronger." Imperial Naruto laughed.

"Worororo… We will! We'll keep getting stronger and reach the ladder's top ten!" Kaido nodded seriously.

After a month training in the Empire, he fully embraced its martial atmosphere, loving it.

This sparked ideas in his mind.

"While getting stronger, don't forget to teach martial arts and chakra training to others." Imperial Naruto reminded.

"Of course, we won't hide it. We'll boost the Beasts Pirates' strength, starting with Wano Country, conquer the world, then join the Empire to face the Otsutsuki! We'll keep this mission in our hearts!" Kaido said frankly.

"Good to know. Our enemy is the Otsutsuki!" Imperial Naruto said, his expression briefly serious, then smiling again. "Also, if you can send us some Devil Fruits for research, that'd be great."

"Worororo… Don't worry, Naruto-sensei! The Beasts Pirates have plenty, especially Zoan-type Devil Fruits. I'll send them once I'm back." Kaido promised.

"Hahaha! Thanks, Kaido. But stabilizing a time-space wormhole isn't easy. Even with our tech, it takes a month, which in your world is four to six months. So, after returning, keep an eye on the time-space vortex's location." Imperial Naruto added.

This shocked Kaido and King, their faces showing surprise.

King said, "What do you mean? This world and ours have different time flows? A month here is four months to half a year in ours?"

"Exactly. Different worlds have different time flow ratios. Didn't I mention? Hm… guess I forgot!" Imperial Naruto blinked, scratching his head awkwardly.

Kaido and King exchanged looks, their expressions grim.

"This is trouble… I didn't expect we'd be gone from Wano so long. Who knows what chaos has erupted." Kaido muttered.

"What's wrong? Trouble back there?" Imperial Naruto asked.

"Sorry, we need to return immediately. The Beasts Pirates occupy Wano Country. Though it's been years, rebels remain. Us being gone so long, those people might not stay quiet…" King explained, glancing at Kaido.

Kaido rubbed his club, grinding his teeth, muttering.

Imperial Naruto showed understanding. "Got it. I'll send you back."

◆━⊰✧⊱━◆

One Piece World, five months after Kaido's disappearance.

Wano Country, a barren, ruined land.

A shrill cry rang out:

"Beasts Pirates scum! Leave Wano! This is the land I, Kozuki Oden, will protect! Thunder Bagua!"

A kimono-clad woman, white flames clouding her back, with pale skin, red horns, and a blue-white tail, struck a mammoth, sending it flying.

"Follow Miss Yamato! Drive out the Beasts Pirates! Protect our country!" An elderly, thin man swung his sword, forcing a tall woman with a spider lower body to retreat, shouting.

"Everyone! Follow Lord Hyogoro! Reclaim our Wano! Expel the Beasts Pirates! Defeat Kurozumi Orochi!" Other samurai shouted loudly.

"Damn it! If Kaido were here, this wouldn't happen! Yamato, you brat! Are you really betraying Big Bro Kaido like this?" Queen, transformed into a yellow brachiosaurus, swung a greatsword at Yamato.

Yamato countered with Thunder Bagua, blasting Queen hundreds of meters away.

"I told you! I'm Kozuki Oden! I'll protect my country and people! Beasts Pirates, leave!" Yamato roared.

"Peerless Frost Slash!"

Yamato opened her mouth, a terrifying icy breath spewing out, freezing most Beasts Pirates and Orochi's men in place.

"Damn brat! When Kaido returns, he'll teach you a harsh lesson!" Queen growled furiously.

His eyes scanned the chaotic battlefield, dizzy with frustration.

In the five months since Kaido and King vanished, things were fine at first. But as their absence prolonged, Wano descended into chaos!

First, somehow, the imprisoned Hyogoro was rescued, leading samurai to ally with Yamato.

Then, someone removed Yamato's cuffs and shackles!

The fighting broke out!

Initially, Queen didn't care. Even without Kaido and King, the Beasts Pirates had two All-Stars, several Tobi Roppo, and many pirates.

Such combat power was formidable even externally.

But once the fighting started, Queen realized his grave mistake!

Yamato, Kaido's daughter, had extraordinary combat strength.

He'd never faced her directly before.

Now, even allied with Jack, they were thoroughly beaten by Yamato.

Her strength far surpassed King's.

This left them unable to defeat Yamato, who could still attack others.

Though they wouldn't lose quickly, if this continued, Wano would fall into chaos!

At this point, it was three to nearly four years before Luffy faced the Beasts Pirates.

Many figures hadn't joined the Beasts Pirates, and many strong fighters were still young, their strength not yet at its peak.

This made the situation extremely awkward.

"Kaido won't return! If you're scared, leave!" Yamato shouted, swinging her club, sending another foe flying.

No one could last long against her.

"Damn it! Why's Kaido's daughter so strong?! Stop her! Are we really losing to this woman and those idiots?"

"What the hell!" Orochi, transformed into an eight-headed serpent, roared frantically, his expression anxious.