Tsunade moved fast. She went to see Sarutobi Hiruzen that very day.
In the Hokage's office, the pipe ember pulsed in the light, smoke blurring his furrowed brow.
"Are you serious?" He asked her a third time. "That kid is Uchiha, and he is likely the clan's future head."
Tsunade slapped the desk, making the ink bottle jump. "Yes. He will be my student. Settled."
Hiruzen felt his temples throb. First Danzō, now Tsunade, each more outrageous than the last.
He set the pipe down and tried one more reasoned appeal.
"You know what this implies. Senju and Uchiha..."
"Senju disbanded, and I do not even carry the name."
Arms folded, Tsunade cut him off.
"Fine."
Knowing he would not move her, Hiruzen sighed and nodded, granting a reluctant approval.
Satisfied, Tsunade left the smoke-choked room at once.
...
Next morning, at Konoha Hospital.
Dragged in to play assistant, Uchiha Jin stood by Tsunade with a helpless face while she treated patient after patient with practiced ease.
Her fingers danced. Green medical chakra flowed. Wounds gaping to the bone closed at a speed the eye could follow.
Most patients felt no pain before she was already finished.
Jin's Sharingan slid open on its own, three tomoe spinning as he studied every nuance of her near-perfect control.
"Well? How much did you understand."
Tsunade asked without looking back.
"About seventy to eighty percent."
The tomoe turned, branding each detail into memory.
"Seventy to eighty. You sure love talking big."
She tossed him a pair of gloves.
"If you got that much, you try."
She nudged him to the table.
Jin glanced at the patient. A through-and-through, not near a vital organ. No wonder she dared let him handle it.
He did not balk. He stripped the gloves and pressed his hand to the wound.
"Wait, you—"
Tsunade moved to stop him. Medical-nin can work bare-handed, but Jin was no medic. She had tossed him gloves to do standard disinfect-and-dress care. He went straight in.
Before she could finish, Jin lifted his palm.
"All done."
The savage wound was gone, replaced by smooth skin without even a scar.
"What is this. What did you just do."
Tsunade clamped a hand on his head and demanded.
"Isn't this the medical ninjutsu you taught."
Jin put on an innocent face.
"The medical ninjutsu I taught. Fine, keep going."
Nearly laughing from anger, she waved for the next patient.
Jin repeated the same action. Wherever there was a wound, he touched it.
No need to judge type, size, infection. In an instant, the patient was whole.
From a haunted stare, Tsunade's expression slid into numbness.
She watched Jin work like an assembly line, not even changing his motion. Later he skipped even placing his palm on the injury. A casual touch anywhere, and every wound across the body visibly knitted.
This was neither science nor ninjutsu. Medical arts only accelerate healing and must be tailored. Some cases require debridement or cutting necrosis. Massive wounds demand sutures. Even her self-made S-rank could not blithely cure every injury like this.
Worse, Jin showed no chakra drain at all. His complexion never changed. Even with Katsuyu assisting, Tsunade could not reach this level.
Only when the last patient left did she snap from the trance.
She grabbed Jin's head with both hands and crushed him to her chest.
"Explain. Properly. Brat, how did you do that."
"I treated normally, okay."
Feeling the pressure at the back of his head, Jin wriggled free and faced her with a solemn look.
"You call that normal."
Her face twisted. She slammed his forehead into her chest again. This time, face-first, he nearly suffocated before he broke loose.
"Talk. Now, you little perv."
Jin raised his hands.
"It really is not medical ninjutsu. Call it my personal gift. Like the Sharingan."
He drew a kunai and slashed his own hand.
No blood. No wound left behind.
Tsunade's face changed. She had seen it clearly. The blade had cut him, but the injury sealed the instant it appeared, as if the kunai had done nothing.
At that speed, she knew only one man to compare with: the God of Shinobi, her grandfather, Senju Hashirama.
"A kekkei genkai. Are you really Uchiha."
"Of course. Hard to fake a Sharingan."
He bared three tomoe to prove it.
Seeing them, her expression grew stranger.
"Your parents. Any outsider in the bloodline."
"Both Uchiha. Clan registry would show it. Why ask."
Jin blinked with feigned confusion.
"It is nothing. Just confirming a few things."
Doubt clouded her eyes. She started packing up on the spot.
She would go ask a few elders about old Senju marriages.
At the door, she paused and pointed back at him.
"Report tomorrow as usual. Or I will have the Uchiha dragged in by myself."
She bolted without looking back.
Had she turned, she would have seen the meaning-laden smile on Jin's face.