During the next years of his life, Reigetsu tried as hard as he could to make Gengetsu finish the peace treaties his father started years prior. Only after the foundation of Konohagakure did Gengetsu decide that it was time to come together and form a Hidden Village themselves. It took two years after Konoha's creation for Kirigakure to be complete after various negotiations.
With Kirigakure in place, Hayami and Reigetsu were finally able to be friends like they wished they could, and they found a perfect harmony in their everyday lives together. Shortly after the village was formed, they decided to live together somewhere in the middle of the city, being away from both of the families that kept them away from each other (although neither of them hated their own clans).
A few years later, the First Hokage of Konoha decided to sell the tailed beasts that he collected, and Hayami, being the bodyguard of the First Mizukage, had to go with him. Every clan that was under Kirigakure had to send one shinobi with the First Mizukage envoy. Reigetsu managed to convince Gengetsu to send him with them.
After the meeting, the clans' representatives and the First Mizukage had a meeting on how to decide who becomes the jinchuriki. Surprisingly, without Reigetsu even involving himself in the conversation, the clans decided that the Six Tailed Beast would most like work the best with a Hozuki Jinchuriki as the beast was known to have a Water Chakra affinity. The Hozuki clan had to decide which members would become its' Jinchuriki.
After a meeting with the clan elders upon their arrival back in Kirigakure, they decided that a newborn would be the best choice for the tailed beast, which Reigetsu totally disagreed with. The moment he made his comment, the whole room went silent, which made him realise that they were too scared to allow a tailed beast inside their own bodies, so he offered himself as a test experiment to see how the Six Tails Beast would react to being sealed inside a human.
With the Six Tails sealed inside him, Reigetsu fell into a deep sleep for about seven days. When he woke up, he felt rage and pain for the tailed beasts that were captured by Hashirama Senju.
Three years later, Gengetsu became the Second Mizukage, and he established the Kirigakure Academy, and then assigned Reigetsu as a leader for a new generation team of three, while Hayami was appointed as the Mizukage Aide.
During that period, Reigetsu almost ended up being forced to marry a woman chosen by the elders, however he refused and said that he would flee the village if they kept going on about something as atrocious as that.
A few years later, at just 54 years old, Gengetsu dies after a battle against the Second Tsukikage. Hayami became the Third Mizukage. Gengetsu's son became the head of Hozuki clan. Reigetsu was finally left alone by the elders. His new problem was Hayami who was barely home because of his new position as Kage.
During one of his missions with another generation of genins in his hands, he found a young child injured when coming back home. He decided to take the child to Kirigakure and take care of him. He named the child, who didn't even know his own name, Naoto.
At 58, during the First War, Reigetsu lost his life, and Naoto became the next Jinchuriki.