Leisure time never lasts long.
After a seven-day vacation, Kakashi returned to his usual training grounds, fully recharged—well, at least physically.
"Tsunade-sensei, we're here."
Tsunade glanced over at Kakashi and Rin, giving a small nod.
More than two years had passed since she began mentoring the pair. Gone were the days of youthful clumsiness. Now, both exuded the calm precision of trained medics.
Kakashi's talent spoke for itself. As for Rin, her control over chakra had blossomed spectacularly.
Through relentless, almost fanatical study, Rin had mastered foundational and intermediate medical theory. And most impressively—she had successfully learned the A-rank medical ninjutsu: Mystical Palm Technique (Shōsen Jutsu).
That was no small feat.
Ninjutsu, after all, wasn't just about flashy explosions. Techniques were ranked according to difficulty and complexity—and A-rank was no joke.
Most shinobi who could handle A-rank jutsu were Jonin-level. Some got access via clan techniques. Others had to trade blood, sweat, and a mountain of mission points just to read an A-rank scroll.
And even if you got your hands on one? Doesn't mean you had the skill to make it work.
Naruto's Multiple Shadow Clone Jutsu, for example—also A-rank. Mostly because anyone lacking a massive chakra pool would die before finishing their cool ninja pose.
Mystical Palm, on the other hand, demanded insane chakra control. A technique so precise, it could repair ruptured organs—but if your focus slipped? You'd do more harm than healing.
That's why only a handful in the entire medical corps could pull it off.
But Rin?
She'd gone above and beyond.
Two years of training with water-chakra control balls in her free time—until she could simultaneously suture a wound and puppet two sparring chakra blobs of Obito and Kakashi on her shoulders.
Yeah, that's right. Medical multitasking jutsu. Patent pending.
Even Tsunade was stunned the first time she saw it.
So the day Rin mastered Mystical Palm, Tsunade officially accepted her as a direct disciple.
"You've both completed the foundational stage of becoming medical-nin," Tsunade said, her tone firm, but a glimmer of pride in her eyes. "From today, you and Shizune will begin internships at Konoha Hospital."
"During the day, you'll work at the hospital. At night, you'll continue advanced training with me."
"Real combat doesn't care how many books you've read—only how many lives you can save."
"Yes, Tsunade-sensei!"
Kakashi and Rin exchanged a glance and replied in unison.
But just as the mood settled...
"Tsunade, have you reconsidered what I mentioned before?"
A hoarse voice cut in like a scalpel.
Kakashi blinked and turned to see the speaker.
Pale skin. Slitted eyes. Snake vibes from twenty paces.
Orochimaru.
Oh great. This guy.
"Reconsider what?" Tsunade's expression darkened.
"The experiment," Orochimaru said smoothly. "Progress has... stalled. I could really use your expertise."
Experiment?
Kakashi's interest sparked. He knew exactly which "experiment" this was.
After the Second Shinobi War, Konoha's strength took a nosedive. The loss of Sakumo Hatake—a Kage-level asset—only made things worse.
In response, the higher-ups launched the infamous Wood Style Experiment, desperate to recreate the unmatched power of Hashirama Senju, the First Hokage.
And no—this wasn't some back-alley side project.
This was fully sanctioned by the Third Hokage himself.
Even the Senju clan members who volunteered did so out of loyalty and belief in the Will of Fire. Noble intentions, tragic results.
Because so far? Zero successes.
Every subject who'd received the First Hokage's cells had ended up overwhelmed by the sheer vitality—and, well, turned into oversized shrubs.
It was a classified project, of course.
But Kakashi and Rin, as Tsunade's close disciples and known for their maturity and silence, were among the few privy to it.
Only the first time Orochimaru visited had Tsunade gone through the motions of secrecy. After that, she didn't bother.
Her face was cold now.
"Orochimaru. I've already told you. I won't stop you—for the sake of the village," she said bitterly. "But I won't participate in something so reckless. Not when it endangers our own people!"
Tsunade wasn't against experimentation. Far from it—she believed medical progress sometimes required risk.
But even she had limits.
Especially when she knew firsthand the terrifying nature of Wood Style. That wasn't a power mortals could just inherit.
And the fact that her fellow Senju had been lining up to "volunteer," only to die one by one?
That made her stomach turn.
Konoha's upper brass had turned human lives into firewood—and the Will of Fire into a slogan.
"If you're not willing," Orochimaru said, turning his yellow-eyed gaze to Kakashi, "then let me borrow him as an assistant."
His lips curled. "He's smart. Adaptable. Promising."
Bingo. That's what he'd come here for all along.
Tsunade's eyes went wide. "Absolutely not! I won't let Kakashi set foot in that lab!"
"Well—actually," Kakashi interrupted lazily, "I kinda want to try it."
Silence.
Tsunade's head snapped toward him. "Kakashi, do you even know what you'd be getting into?!"
"Do you think our comrades are just stepping stones on the path to power?"
Kakashi met her gaze calmly. "No, Sensei."
"But if the experiment's going to continue either way... maybe I can help make it less deadly."
"If I can use the medical skills you've taught me to give even one of them a better chance to survive, isn't that worth it?"
Tsunade stared at him, searching for any sign of falsehood. She found none.
The words weren't rehearsed. Just honest.
Reluctantly... she had to admit—he wasn't wrong.
She still hated the experiment. But if it had to happen, then maybe Kakashi could reduce the number of corpses piling up behind it.
Orochimaru, standing off to the side, remained quiet.
But inside, his interest in Kakashi had just gone from curious to obsessive.
Finally, Tsunade sighed. "Fine. If you really want this... I won't stop you."
"But there are conditions!"
Her finger jabbed the air like a kunai.
"You must attend advanced medical training every single night—no skipping."
"And if you run into anything you can't solve in that lab, bring it to me during class."
"No experimenting alone. Got it?"
"Got it, Sensei!"
Kakashi exhaled quietly in relief.
Finally. Official permission to observe the Wood Style experiments—and access to Hashirama cells.
Orochimaru gave a thin smile and turned to leave.
Kakashi followed.
But just as they stepped out the door, Tsunade's voice rang out one last time.
"Orochimaru."
He paused.
"Whatever happens—protect him."
Orochimaru didn't turn around.
But the words hit him harder than expected.
They echoed something he'd heard long ago—when Nawaki left on his final mission.
Back then, he hadn't kept his promise.
And Tsunade had lost her little brother.
Now, her words carried weight.
"Don't worry, Tsunade," Orochimaru murmured, eyes narrowing."This time... I won't fail you."