The Third Mizukage stepped down partly because his own foolishness caused the Blood Mist to make too much noise, and partly because Madara Uchiha used Genjutsu on the Third Mizukage.
However, after teaching Obito the use of the Sharingan and the forbidden techniques of the Yin-Yang Release, Madara Uchiha died.
Yet before Madara Uchiha died, he specifically mentioned two people who were obstacles to the plan: Kushina Uzumaki and Nawaki.
One was very similar to the previous Nine-Tails Jinchuriki, capable of using massive tailed beast power, and even if Obito Uchiha awakened the Kamui Eye Technique, he might not necessarily be able to deal with Kushina Uzumaki.
There was also Nawaki, who could use the Wood Human Technique at this age. Even though Madara Uchiha was unwilling to admit it, Nawaki's current Wood Release ninjutsu was already similar to Hashirama Senju at this age back then; what he lacked now was Senjutsu.
If these two people were not dealt with, the Eye of the Moon Plan would likely not succeed.
The Kamui dojutsu was a bit wondrous, but it was not invincible. Unless Obito Uchiha was willing to take back the other eye on Kakashi, it would be very difficult for him to make a move against those two people.
Whether it was Nawaki's caution or Kushina Uzumaki's mastery over the tailed beast power, either was enough to make Obito Uchiha's Kamui Eye Technique fall flat.
The childbirth of the Nine-Tails Jinchuriki is indeed an opportunity, but relying solely on Cloud Ninja and Kirigakure is probably not enough.
Obito Uchiha pondered in his heart. He was still thinking about the Eye of the Moon Plan mentioned by Madara, intending to mess with Kirigakure for revenge along the way while executing this plan, and moreover, Kirigakure's strength also held a fairly