Each morning, Black Ape began by filling his Ten Seal to capacity with chakra.
After allowing his body and natural reserves to recover, he would extract the stored chakra in one explosive surge.
The stimulation coursed through him—muscle, bone, and tendon awakened with power.
His entire body brimmed with chakra, air currents swirling around him like a second skin.
But he didn't unleash it.
His chakra volume still corresponded to his physical constitution. At his current strength, that was his limit.
Then, he formed hand seals and released the Ten Seal.
The chakra surged from the back of his hand like a flood—threatening to burst his body apart.
But it was his own chakra—previously extracted—so his body didn't reject it.
Had it been forced in by someone else, especially non-healing chakra, he would've been in serious danger.
This was too much chakra.
It pounded through his muscles, bones, and internal organs like a roaring river.
After enduring the strain for a while, Black Ape formed hand seals and poured the chakra out in a massive jutsu: Earth Release: Earth Longspear – Thorn Forest.
Jagged spears erupted in tangled clusters, forming a bramble field several meters high, spanning dozens of meters in every direction.
From the sidelines, Yako nodded with approval. "Not bad. That Earth Longspear almost has a trace of my own flair."
Black Ape collapsed to the ground, panting hard.
It took nearly half an hour to recover from the chakra overdraw.
Three sessions like this per day—that was the extreme stimulation training Yako had designed for him.
Yako stood nearby, watching and recording every detail.
He had no idea whether this would truly help Black Ape break through his physical ceiling. Both were still experimenting, feeling their way through the dark.
If Orochimaru were here, he'd probably have figured out the optimal stimulus pattern in no time—because he wouldn't care if the test subject died in the process.
While the rest of the squad handled missions along the border, Black Ape had received special permission to remain in camp for focused training under Yako's supervision.
After fifteen days of hellish practice, Black Ape burst into the tent, eyes blazing. "Captain! I'm getting stronger again! My chakra reserves are growing!"
Yako had him demonstrate.
Even without using the Ten Seal, his Earth Release techniques had expanded in scale.
"Now, let's test your taijutsu. Let's see if your physical stats have improved."
They sparred.
Yako confirmed it: Black Ape's strength and speed had both clearly increased over the last two weeks.
But something was off.
"Wait," Yako frowned, stepping back. "That arm swing just now—feels wrong."
He halted the match and had Black Ape roll up his sleeve.
There it was. Muscle damage.
"Looks like this stimulation has side effects. You'll need to pair it with medical ninjutsu from now on."
Yako led him to the medical tent.
"You need a proper evaluation," he said. "Let's hear what the medic says."
Training might make you stronger—but it could also break you down.
Without a teacher or medical support, reckless practice could leave you with a body full of lingering injuries.
Many Konoha shinobi trained themselves to death—overworked and stiff, falling to a stray kunai they should have easily dodged.
The camp's lead medic was Senju Miraki.
She'd been through a few scandals, but in the end, she'd become a medical jonin.
Yako felt a twinge of guilt—she probably didn't know it had been Fox Squad who set up that earlier "medical dispute incident" against her…
Miraki examined Black Ape.
"You're insane," she scolded. "You overextracted your chakra, overstrained your cells, and now your body's riddled with micro-injuries."
She pressed a glowing green hand to his arm and began healing him with Medical Chakra.
It took over twenty minutes.
"Try stretching," she instructed. "Arms back, spine twist, full bend."
Black Ape moved. Everything was smooth again.
The lingering damage was gone.
As they left the medical tent, Yako muttered, "I thought it was just a pulled muscle. Didn't expect cellular fatigue-level microdamage."
"Black Ape, no more three-a-day sessions."
"Durability is a kind of talent too—and your body isn't built for it."
"You need to pace yourself. Train every two or three days instead. And check in with the medics regularly."
"I gave you the Ten Seal to make you stronger—not to send you to the morgue."
Black Ape raised his hand. The Ten Seal on his hand was hidden beneath his glove.
"Captain, three months ago I realized I'd hit my limit. No matter how hard I trained, I couldn't improve. I felt hopeless. I was terrified—every day."
"Everyone around me was growing, getting stronger. I was the only one standing still."
"I started avoiding sparring matches. I didn't want anyone to notice."
"You gave me hope, Captain. You showed me that effort still matters. So what if I pick up a few injuries?"
"I've never felt more alive. Thank you."
Yako replied, "I'm not saying don't train hard—I'm saying don't overdo it."
"Work smart. Minimize your burden. Heal your wounds properly. Improve steadily."
"If you get reckless again, I'll remove your Ten Seal myself."
"Please don't!" Black Ape panicked. "I get it, I promise. I'll only train every two days, no more! No more overdoing it!"
Yako chuckled. "You've been with me for over a year now. We fought in the Land of Rivers, the Land of Whirlpools."
"For ANBU in wartime, surviving a year is already an accomplishment."
"I want you to keep surviving. Not become another name on the casualty list."
"You're one of the subordinates I trust the most. Don't throw that away just for power."
Men didn't need flowery speeches.
Black Ape bowed his head.
He swore silently: he would never betray that trust.
"Alright," Yako said. "Go find White Ram and Blossom Deer squads. We're heading out."
"Yes, sir!"
In the ANBU tent zone, Yak—known for his Earth Release—felt a tremor beneath his feet. He sensed it was the two squads using Body Flicker.
He turned over and went back to sleep.
'Must be some special mission.'
Before long, both squads arrived at an open field outside the camp.
They noticed something odd: they weren't heading to the frontlines.
Instead, they followed Yako into a flat clearing nearby.
Yako sat on a boulder and looked at them.
"I'm sure you've all noticed I've been sneaking around with Black Ape lately."
"I've been working on something. A new seal. Something that can increase your strength."
"I call it the Ten Seal."
"You've all fought beside me through multiple wars: Grass, Rain, Rivers, Whirlpool, and now Hot Water."
"I was going to set a test—but forget it. Your records speak for themselves. You've earned this."
"The Ten Seal will be our signature technique—our bond."
"Black Ape, show them what you've gained."
The squad's hearts pounded.
Fox Squad's captain was already viewed as elite jōnin level. A man worthy of crafting powerful techniques.
And now, he'd mastered ANBU sealing arts and revealed his own talent in developing custom jutsu.
Excitement surged.
Just how powerful was a seal… designed by a shinobi like that?