At first, Uchiha Yi had considered helping Kushina Uzumaki learn Sage Mode.
Over the past three years, Tsunade had gained a basic grasp of Sage Mode. After all, she had Hashirama Senju and Uchiha Yi helping her, and her own chakra reserves were enormous. Well, as long as she was not pouring them into that Yin Seal, she really did have plenty of chakra. Her chakra control was also among the best in Konoha. Perhaps the original Tsunade had gone down the wrong path, disliked the slimy feeling of slugs, or been frightened by Jiraiya's appearance in Sage Mode. Or perhaps she simply had no ambition to grow stronger. Whatever the reason, she had never trained in Sage Mode.
Now, however, with Uchiha Yi and Hashirama Senju's help, Tsunade had gained a basic grasp of Sage Mode in just three years. Although she still needed the Slug Sage's assistance to enter it, unlike Uchiha Yi and Hashirama Senju, that was already quite impressive. At the very least, her strength had increased significantly.
Orochimaru had also researched Sage Mode, but after studying it for a while, he reluctantly discovered that he could not do what Tsunade and Jiraiya did. His chakra reserves were still insufficient. Perhaps he also had too much on his mind to settle down completely and sense natural energy. Nor did he have snakes from Ryūchi Cave helping him absorb natural energy the way Katsuyu and the toads did. His desire to master Sage Mode only grew stronger.
I have to learn Sage Mode, but first, I need to make my body more compatible with natural energy.
Orochimaru was modifying his own body while also modifying White Zetsu.
Working under Uchiha Yi gave him the best research material, abundant resources, and Tobirama Senju, a senior researcher ahead of