A hero arrives, a seven-day pledge

Shamon, the Second Kazekage, was a highly capable leader.

He was probably the first ninja in the shinobi world to try using tailed beasts in warfare.

Although he had yet to create a perfect Jinchuriki, his efforts had allowed Sunagakure to establish communication with the Three-Tails well before the war began.

Isobu had long since grown sick of the constant lack of water, and his temper had become exceptionally volatile. Shamon seized the opportunity to approach him, promising to release him from his Jinchuriki someday and provide ample water in exchange for a chance to communicate.

The two sides struck a deal.

Humans could not be trusted, especially ninja. But Isobu clearly lacked experience dealing with humans. Too simple-minded, he readily agreed.

Of course, Shamon was not merely making empty promises.

Using his authority as Kazekage, he poured vast amounts of the Hidden Sand's manpower, money, and resources into constructing an artificial lake deep in the desert for Isobu. He also held the Jinchuriki's family hostage, forcing the host to let Isobu control their body and mind.

Ordinarily, a Jinchuriki needed a tailed beast's approval to achieve complete tailed beast transformation. Under Shamon's arrangements, however, that rule was reversed: the tailed beast now needed its Jinchuriki's acceptance.

Through this forced cooperation, Isobu could spend time in his full form at the artificial lake every day.

Shamon himself was also proficient with poison, and he noticed the unusual properties of Isobu's chakra. He then proposed another deal: upgrades to the artificial lake in exchange for Isobu producing raw materials for poison.

At first, Isobu refused.

It was not that he was unwilling, but that he did not dare. The Sage Hagoromo had expressly forbidden him from harming humans with poison. But the Sage was dead, while the tailed beast was alive.