Tsunade did not activate the Strength of a Hundred Seal and charge in recklessly with Creation Rebirth, because Jiraiya stopped her.
If she activated the Strength of a Hundred Seal, things would go beyond the scope of a sparring match. This one-on-one fight was hardly a life-and-death battle. Rather than suspecting that Tsunade wanted to test Yinsen's strength, it was more accurate to say that she wanted to see just how much Combat Power his Wood Release possessed.
The facts proved that Yinsen indeed had the strength to drive back Orochimaru. Moreover, although his Wood Release differed greatly from that of the First Hokage, it was undeniably Wood Release.
Confirming that was enough!
More importantly, Tsunade had already used Creation Rebirth once during her battle with Orochimaru not long ago. This ninjutsu placed a heavy burden on her—while using it, she was effectively possessed of an Undying Body, but it consumed her lifespan. Frequent use would only bring about her death sooner.
Jiraiya had no desire to see Tsunade sacrifice her lifespan over a sparring match, so he stepped in and ended the fight.
The cherry blossoms that had gathered together slowly scattered, drifting gently down to the ground. As Yinsen stopped his ninjutsu, those blossoms gradually vanished as well.
Sasuke and Naruto, watching those cherry blossoms from afar just like Jiraiya, found Yinsen's fighting style very familiar. It was the same style used by an enemy they had fought not long ago.
"The way Yinsen uses petals... is a little like Gaara..."
"Yeah!"
Sasuke clenched his fists. He recalled the helplessness he had felt when facing Gaara. Back then, no matter how desperately he fought, he had been unable to defeat that terrifying opponent.
Yet Yinsen could use a ninjutsu very similar to Gaara's. Did that mean Yinsen's strength