Question about the hokage on NARUTO?

After the 4th hokage had died, the 3rd was put back into the chair, to make up for the 4th dieing, because they needed a hokage. After the 3rd was killed by Orochimaru, they had to search for another hokage. And that is were Pervy Sage comes in. He and Naruto had to search for Tsunade, how later became the 5th hokage.