After the war the Third Hokage, Hiruzen decided to make Minato the Fourth Hokage. During his reign as Hokage, he decided to integrate Kakashi into the Anbu to better monitor him. He also asked Kakashi to watch over Kushina during her pregnancy. During this same period he was visited by Jiraya the sensi of naruto merch, who thought that his student was the child of the prophecy. It was probably during this visit that Minato and Kushina decided on the name of their child, the same as the Hero of Jiraya’s book, Naruto, which made Jiraya his godfather.
The birth of Naruto Uzumaki took place in a secret place that only Minato, Hiruzen and his wife Biwako knew about. During the birth, Minato’s goal was to maintain the seal because the seal was weakening during the birth. During the birth, the masked man killed the Anbu members who were protecting the entrance of the cave and infiltrated the birth place. After Naruto was born, the masked man killed Biwako and Taji, and grabbed Naruto, threatening to kill him if Minato didn’t get away from the jinchuri.
The seal of Kushina, which was holding Kyubi, was getting weaker and weaker, which worried Minato, who also wondered how the masked man managed to get through the protective field. Tobi ordered Minato to get away from Kushina if he didn’t want Naruto to die. He carried out his threat, but Minato quickly saved his son. However, Tobi had placed explosive scrolls on Naruto, forcing Minato to teleport away. Fortunately, Minato, carrying Naruto in his arms, managed to escape the explosion unharmed. Tobi took Kushina somewhere else, freed Kyûbi and took control of the bijû. He tried to eliminate Kushina, but Minato appeared and saved her. She told him that they were heading to Konoha and that he should stop them. Minato looked at the masked man with a threatening look before leaving. Minato took his wife to Naruto, took his Hokage robe and went to stop Tobi.
Minato in front of Kyûbi.
Minato arrived in Konoha, at the Hokage Monument, and was spotted by Kyûbi who sent him a Tailed Demon Orb. Minato countered the attack with a space-time barrier that sent the bomb away from Konoha, alerting the village to its presence. Minato was then ambushed by Tobi who tried to take Minato to another dimension. Minato used the Flying Thunder God technique to quickly escape. Minato didn’t understand the technique that Tobi had used at first. Tobi reappeared in front of Minato.
Realizing that Tobi’s power and knowledge was abnormal, Minato asked Tobi if he was Madara Uchiwa, but he said that it was impossible, because Madara had been dead for a long time. Tobi speculated otherwise. Minato concluded that Tobi, having a space-time technique superior to his and Tobirama’s, coupled with his ability to control Kyûbi, were too dangerous to be allowed to live. Minato attacked Tobi, but he passed through him and Minato understood how Tobi’s technique worked. With the fight now settled with speed, the two opponents charged towards each other, Minato threw a space-time kunai, which only passed through Tobi and then executed a swirling orb. Tobi grabbed Minato’s cloak, thinking that he had won, however Minato teleported right above Tobi with the previously thrown kunai and hit him with the swirling orb.