Because this technique had yet to be completed, and though Orochimaru's laboratory had also provided assistance, perfectly mastering Natural Energy and synthesizing perfect Senjutsu Chakra was far from simple.
Even the three great sacred lands with their inheritances of senjutsu had only produced a handful of people capable of learning Sage Mode to this day.
Its difficulty was obvious.
What was more, Kusagakure had started from nothing, researching its own technique from Jugō and the Sage Modes known from the three great sacred lands!
The difficulty was even greater!
After spending so many years and investing so much manpower and resources, with the help of Orochimaru, one of Konoha's Sannin, they had only now... achieved some success.
Yet it was still difficult to learn, demanded high physical aptitude, and also had a significant... impact on the body!
And its dangers were still unknown for the time being.
At this moment.
Uzumaki Yangzheng led the team, not daring to relax for even an instant as they continuously collected the incoming data.
Should any danger arise... they would immediately halt the experiment!
Of course~
For Kusana, this technique was less of a Sage Mode and more like the Heavenly Curse Mark created by Orochimaru.
Only, Orochimaru's Heavenly Curse Mark was bestowed through his bite, and afterward required all kinds of secret techniques to alleviate its erosion of the body. Kusagakure's technique... had to be cultivated personally, forming one's own curse mark.
If the body could not withstand the erosion, it would be impossible to complete the cultivation. The process itself was also extremely dangerous and equally difficult!
That this technique had been developed to this point was also thanks to the contributions of Jugō and Kusagakure's friend—Orochimaru.
Though it was not perfect yet, it could still be cultivated successfully.
And speaking of