Yin threw himself into studying Sealing Jutsu, struggling with it every day.
Whenever his progress stalled, Black Zetsu would silently poke his head out from behind him.
He neither criticized nor scolded him. He simply watched without a word, then shook his head in disappointment, sighed, and turned away.
Yin was at a loss over this behavior. He wanted to say something but had no way to explain himself. After all, the problem had started with his own unsatisfactory performance.
Too embarrassed to cling to him and plead his case, he wilted like a little animal caught in the rain, clutching his book as a storm of knowledge washed over him.
He gritted his teeth and devoted more time and energy to Sealing Jutsu. He had never studied so hard before, seemingly oblivious to Black Zetsu's deliberate attempts to distance himself.
Watching him study so diligently without causing trouble, Black Zetsu felt the gratifying warmth of seeing a child finally grow up. Reassured for the moment, he went off to handle other matters.
The most important of those matters was none other than the owner of the Rinnegan, who was slowly coming around.
After days spent unconscious from overusing his Rinnegan, Longjian Senju finally woke up.
His injuries had healed, a Cursed Seal had been placed on his heart, and his chakra had been sealed. He now sat warily in a corner of a dimly lit, soundproof cell.
In truth, he had been awake for some time, but Black Zetsu had deliberately left him waiting.
Judging by appearances, Longjian and Shisui were the same age, and presumably his mind was not yet all that mature either. Using a few little tricks to steer his thoughts astray would be simple enough.
The near-absolute silence inside the cell could severely wear down