The reason Might Duy possessed such overwhelming strength was because he had mastered the Eight Gates Technique.
According to Duy himself, it had taken him a full twenty years to completely master the technique and reach the level where he could open all eight gates.
A few years later, during the Third Great Ninja War, he unleashed that power in a moment of fury—opening all eight gates and turning the fearsome Seven Ninja Swordsmen of the Mist into the infamous 'Three Lucky Survivors.'
Aoshi estimated that even if Duy couldn't open seven gates now, he could still manage at least six.
As a side note, with Might Duy's strength, it was impossible for him to suffer injuries from doing D-rank missions.
And that, indeed, was the case.
After a full examination, Aoshi determined that Duy's condition wasn't the result of combat injuries—but rather, a chronic strain caused by long-term overtraining. Years of pushing his body beyond its limits had finally caught up to him, leading to a temporary collapse that required hospitalization.
As a low-ranking shinobi, Duy's earnings were meager. On top of that, he gave most of his earnings and resources to his son, Might Guy. As a result, he couldn't afford secret medicines or treatments to maintain his health.
Thankfully, in the world of shinobi, this kind of condition wasn't rare—and with Aoshi's medical skills, it was easily treatable.
[Treatment of Might Duy completed. Reward: One Gold Orb.
Congratulations! You have obtained: Eight Gates Technique.]
The system's reward was exactly what Aoshi had anticipated. After all, the Eight Gates were Duy's most iconic and valuable technique.
"Thank you, doctor! Your medical skills are incredible—I can already feel my youth burning again!"
"…" Hearing this, Aoshi's expression darkened slightly.
Now he understood how Hatake Kakashi must have felt, constantly harassed by Might Guy's boundless enthusiasm.
Normal people really weren't equipped to handle this level of 'youthful energy.'
"Your condition is due to long-term overexertion. Please be mindful and avoid intense physical activity for the time being."
Fulfilling his responsibility as a medical professional, Aoshi offered the necessary warning.
Might Duy gave a radiant thumbs-up, flashing a dazzling white grin. "Youth needs rest too!"
Shaking his head in surrender, Aoshi quickly left the treatment room—any longer and he was afraid he might catch the 'Youth Virus' himself.
As fate would have it, he ran into Tsunade, who had just arrived at Konoha Hospital.
"Lady Tsunade! I've mastered the Chakra Scalpel. When can you begin teaching me the Yin seal: One Hundred Healings Mark?"
"…What did you just say?"
"I said, I've already mastered the Chakra Scalpel!" Aoshi repeated his words slowly and clearly.
"You're not just bluffing to avoid losing our bet, are you?" Tsunade still couldn't believe it.
Without further explanation, Aoshi took her to an operating table, selected one of the fish used for practice, and performed the Chakra Scalpel technique right before her eyes.
Seeing it for herself, Tsunade could no longer deny it—Aoshi had indeed mastered the A-rank medical technique in just three days.
It was worth mentioning that many chūnin-level medical ninja had yet to fully grasp this technique. Only a select few elite medical jōnin could wield the Chakra Scalpel with complete proficiency.
From that standpoint, Aoshi's level in medical ninjutsu had already reached jōnin class.
Becoming a medical jōnin at the age of eighteen wasn't unprecedented. But what was truly astonishing was that Aoshi hadn't even touched medical ninjutsu before the age of seventeen—and in just one year, he had risen this far.
Even Tsunade couldn't help but be stunned by Aoshi's extraordinary talent.
This was the true mark of a genius.
"…Fine. You win. Here's the scroll for the Strength of a Hundred Seal." Tsunade was not a sore loser. She handed over the scroll without hesitation.
"Yin seal: One Hundred Healings Mark is an S-rank technique. With your ability, you should be able to master it in three to four days."
After instructing him, Tsunade didn't leave right away. She made her way to Minako, who was now in charge of Konoha Hospital's internal administration.
"Minako, from now on, make sure to focus on cultivating Aoshi. His potential is on par with mine."
Tsunade wasn't referring to training in medical ninjutsu. She meant leadership development.
In her eyes, Aoshi had what it took to succeed her as Head of the Medical Corps one day.
In fact, had he been a little older and more experienced, she might've already handed over the position and walked away without a second thought.
That way, she could gamble freely, day and night—
Cough. No, that wasn't the point.
The point was: as a senior, she had the duty to make room for the next generation and help them grow. Yes. That was it.
"I understand, Lady Tsunade." Minako fully grasped the meaning behind Tsunade's words.
And because she understood, she was shocked. She had already regarded Aoshi with high expectations—but now realized she had still underestimated him.
---
After receiving the Yin seal: One Hundred Healings Mark, Aoshi returned to his office.
Instead of jumping right into studying the new technique, he first checked the system reward: Eight Gates.
Every person possesses eight internal gates in their body—natural limiters that regulate chakra flow. These gates serve as the body's built-in safety mechanisms.
The Eight Gates technique allows one to forcibly release these limiters, unlocking incredible power at the cost of severe physical stress.
It was a form of pure taijutsu, removing the body's natural chakra restraints.
The eight gates are: Gate of Opening, Gate of Rest, Gate of Life, Gate of Pain, Gate of Limit,
Gate of View, Gate of Wonder, and the Gate of Death.
Each gate opened boosts strength dramatically.
For example, opening the Gate of Opening removes mental inhibitions, allowing the user to utilize 100% of their body's potential.
But the final gate—Gate of Death—grants godlike power, surpassing even the Kage-level.
Of course, the results vary depending on the user's talent and physical ability. For instance, even after opening all eight gates, Might Duy was only able to eliminate four of the Seven Ninja Swordsmen.
But his son, Might Guy, was in a league of his own.
During the Fourth Great Ninja War, in a battle among demigods, he opened all eight gates and nearly turned the tide of war.
Even Uchiha Madara, in his Six Paths form, acknowledged: "In taijutsu, you are the strongest."
Some even claimed taijutsu wasn't something everyone could truly master—only Might Guy could truly embody it.
"Even with this system reward, given my current physique, I can only open the first gate."
Unlike ninjutsu or genjutsu, taijutsu relies entirely on the body. The system couldn't cheat biology. If the user's body wasn't conditioned, opening additional gates would result in self-destruction.
If Aoshi hadn't been diligently training in swordsmanship, he probably wouldn't even be able to open the first gate now.
"Looks like I'll need to include daily physical training from now on." Now that he had the Eight Gates, Aoshi had no intention of letting them go to waste.
He didn't aim to reach the level of Might Duy or Might Guy, but opening up to the sixth gate was a worthy long-term goal.
Only then would true transformation begin. Of course, it would take time.
After his shift ended, Aoshi immediately started his physical training regimen.
He began with two laps around the village, then returned to his usual training ground to begin practicing Yin seal: One Hundred Healings Mark.
The reason he only ran two laps was simple—he had just started and didn't want to push himself too hard too soon.
Overtraining on the first day would be counterproductive—just like what happened to Might Duy.