The next day – Orochimaru's laboratory.
The compatibility with Hashirama's cells had reached a whopping 50%.
Kakashi frowned as he read the data.
Because of Yamato's unexpected success, Orochimaru had developed a fresh obsession with engineering an upgraded version of the Wood Style. He was now trying to find a shortcut—one that wouldn't require a Senju bloodline lottery ticket.
So all previous mass villager-screening experiments had been shelved, and the new focus? Kakashi's own genetic material.
Fifty percent compatibility. In other words, nature was sending a polite "no thanks" to the Hashirama infusion. Even if the fusion somehow succeeded by sheer luck, Kakashi would be walking a tightrope—forever on the brink of cellular rebellion.
And when that rebellion starts, guess who loses?
Danzo in the original timeline looked like a rotting tree stump with a sharingan arm patchwork quilt. All that, just to barely hold the Wood Style's tantrums in check. Spoiler: Didn't end well for him.
Kakashi had zero interest in turning into a chakra-infused science experiment gone wrong.
So, he shelved Plan A and decided it was time to activate his backup.
After leaving a Shadow Clone in the lab—half his chakra gone, but hey, multitasking—Kakashi made his way toward a certain office.
"Tsunade-sensei, you in?"
Knock knock.
"Mm? Kakashi? Yeah, come in."
Tsunade's voice came through the door, laced with lazy drowsiness.
Kakashi stepped inside and immediately paused.
Oh.
The red sleep marks on Tsunade's cheeks were still fresh. Water stains at the corner of her mouth suggested she had either been mid-dream… or sleep-drooling like a champion.
Huh. Guess being the dean came with perks—like napping in broad daylight. Must be nice.
Tsunade cleared her throat and subtly wiped her face. "Ahem. What brings you here at this hour?"
"I want to go to the Shikkotsu Forest," Kakashi said plainly. "To learn Senjutsu."
Tsunade blinked. "You want to learn Sage Mode?"
"Yes."
"You do know it's incredibly dangerous, right? If you mess up, it's game over. People have died trying."
"I know. I'm prepared."
Tsunade studied him for a moment, then sighed. "Well… if it's you, maybe you have a shot."
She took him to the courtyard and unsealed a scroll with a flick of her wrist.
"This is the contract scroll for the Shikkotsu Forest. Sign in blood, summon Katsuyu. Let's see how big a clone you can call forth."
"And be respectful. Katsuyu is part of the Sage—so no poking, squishing, or… anything else weird."
Kakashi nodded solemnly.
He channeled chakra into his left hand and nicked the index finger of his right. With blood, he signed: Hatake Kakashi.
Boom. Contract complete.
He already had the Hatake clan's summoning technique, so this was more of a multi-pack upgrade.
Distinguishing between contracts? Easy—just think of the desired summon by name. Chakra would do the rest.
He clapped his hands together.
"Kuchiyose no Jutsu!"
BOOM!
Smoke exploded around him. The next thing he knew, he was no longer standing on solid ground—but on something soft and squishy.
Below him, a building-sized slug.
Kakashi poked the surface.
Soft. Elastic. No slime. Just a gelatinous jelly texture.
Better than expected. Honestly, anime had really oversold the slime thing.
A gentle, feminine voice greeted him. "Lady Tsunade, what do you need?"
Katsuyu's massive eyes scanned the area—no injuries, no chaos.
Kakashi's summon size had impressed her, and it showed in Tsunade's rare nod of approval.
"I didn't summon you this time," Tsunade said. "This is Kakashi, your new contractor."
"Oh? A pleasure, Lord Kakashi," Katsuyu said politely, bobbing her antennae.
"Ah! No need for the 'lord' thing. I haven't even graduated ninja school yet," Kakashi said quickly, waving his hands.
"It's customary," Katsuyu replied calmly. "A sign of respect."
"Yeah, yeah. Names are whatever," Tsunade cut in. "Let's get to business. Katsuyu, take us to the Shikkotsu Forest. Kakashi wants to train in Sage Mode."
Katsuyu gave a small nod. Poof! Space warped, and Kakashi felt like he'd been sucked into a swirling vortex.
The moment light returned—
"Whoa…"
Kakashi stood in the mystical Shikkotsu Forest.
At a glance, it was stunning—verdant mountains, lush trees, and a sea of green that swayed like waves in the wind.
But look closely?
The upper halves of the trees were vibrant, yes. But the lower halves…?
Thin. Pale. Bone-like.
Creepy.
A massive Katsuyu lay atop one of the trees, munching calmly. Kakashi did a quick estimate—at least 3,000 meters long.
"That's my true body," the smaller Katsuyu explained. "This forest is my pantry."
Well. That explained the vibe.
No birds chirping. No bugs buzzing. Just quiet. Too quiet.
A voice—deeper, wiser—rumbled through the clearing.
"Welcome, young Tsunade. Young Kakashi. This is my domain."
The real Katsuyu Sage was speaking through the clone now.
"Apologies if I don't speak directly. Eating is life's truest pleasure, and I indulge slowly."
Kakashi bowed his head. "Please don't mind us, Sage. Continue your… brunch."
He felt a flicker of amusement from the Sage. Good start.
"Kakashi-chan," Katsuyu Sage said, "Tsunade should've explained this, but let me clarify. Senjutsu is the fusion of physical energy, spiritual energy, and natural energy in a perfect 1:1:1 ratio."
"When you achieve this balance, you enter Sage Mode. In that state, your Ninjutsu, Taijutsu, and Genjutsu receive massive amplification."
"And," the Sage added, "the Shikkotsu Forest's unique style also greatly enhances regeneration."
Tsunade's eyes lit up. "Like my grandfather, Senju Hashirama?"
"Yes. He trained here, long ago. Hashirama was… exceptional."
The Sage paused, reminiscing. "He was born with a rare Sage physique. Mastered the art in a single day."
Tsunade was quiet. She'd seen her grandfather's might. Kakashi? Genius as he was, comparing him to Hashirama was…
Well. Let's not jinx it.
"Kakashi-chan," Katsuyu Sage said, "watch carefully. I'll show you how to sense and absorb natural energy."
"But listen carefully: natural energy is wild and volatile."
"If you mess up, your body won't just turn to stone, like at Mount Myōboku…"
"You'll turn into me. Or rather, a part of me."
Kakashi blinked. "…Wait. You mean—"
"Yes. All past failures have become part of me."
Kakashi stared at the slug.
So let's recap: mess up in Mount Myōboku? You become a statue. Ryūchi Cave? Snake chow.
Shikkotsu Forest?
Welcome to slug-hood.
Yay.
Still, Kakashi didn't flinch. "I'll succeed. I'm ready."
"…Very well."
Katsuyu Sage began demonstrating the subtle dance of natural energy flow. For most, this process took hours of meditation, trials, and more meditation.
Kakashi?
His eyes glowed golden. Black markings spread around them.
Complete Sage Mode.
Tsunade blinked in disbelief. "You've got to be kidding me."
Katsuyu Sage's body rippled in surprise. "Already? That quickly?"
Kakashi rubbed the back of his head sheepishly. "Uh… I think I got it?"
Silence.
Katsuyu Sage finally murmured, "Even Hashirama took a full day. You… are extraordinary."
"The last one I saw like this was the Sage of Six Paths himself."
The Sage of Six Paths, huh?
Well, Kakashi wasn't interested in divine bloodlines or celestial excuses.
He believed in work. In tech. In copying smarter, not harder.
The path to the peak wasn't about winning the genetic lottery—it was about knowing the rules of the game.
And rewriting them.
"Thanks, Katsuyu-sensei," Kakashi said sincerely. "We're ready to go back now."
"Very well, young ones."
A flash of light—POOF!
They were back in Konoha.