As chakra lifeforms, they were inherently unable to stand alone against the Rinnegan, which could absorb chakra. But fighting alongside jinchūriki allowed them to overcome this fatal weakness.
As a bloodline mutation of the Rinnegan, the Sharingan's dojutsu had the same suppressive and controlling effects on them. This was also the firm condition Konoha had set after discussing the matter with the Nine-Tails—
The tailed beasts could regain their freedom, but in exchange, they had to possess the ability to resist dojutsu control, even control backed by considerably powerful eye power.
The example of the Fourth Mizukage, the Three-Tails' jinchūriki, had been far too tragic.
So although the tailed beasts were ostensibly spending their time roaming the Forest of Death, they were essentially serving time in prison.
And the condition for their release was to overcome the Sharingan of their "Warden," Sasuke Uchiha.
He was also currently Konoha's foremost wielder of kekkei genkai dojutsu. The Hyuga Clan's Byakugan did not possess comparable control abilities.
Although the tailed beasts knew this was for their own good, being kept like pets still deeply irritated the more temperamental ones among them.
So, the moment they learned how to resist the Sharingan, the three tailed beasts led by Shukaku found an excuse to corner Sasuke.
"In that case..." Sasuke raised his gaze, Shukaku's eager, fist-rubbing figure reflected in his Mangekyō Sharingan, then gently closed his eyes.
Susanoo and the Black Flames abruptly vanished, along with Sasuke himself.
This left the excited Shukaku stunned for a moment before he flew into a rage.
He nearly reverted to his true form and struck his belly to fire an Air Bullet that would blow the place apart, but the Two-Tails and Four-Tails beside him hurriedly held him back.
At the exit of the Forest of Death.
Having