Minato had just found a scroll, one forbidden scroll which allowed to bring people from the future to the past and he had just the people, he wanted to test it by sending himself and some others to the future.

He was going to use it to see the future and see what had become of him, his child and his now-pregnant wife, Kushina Uzumaki.

However he wasn't alone in this as Hiruzen much time after his death too, wanting to see the fate of the Jinchuriki, Naruto Uzumaki and Sasuke Uchiha. It would be to see if his efforts were in vain.

In another time, the first Hokage and his younger brother along with the Uchiha Clan leader, Madara Uchiha himself wanted to see if peace was obtainable, if the clans had been united, he wanted to see if their dream had been achieved.

They all activated the seal, with certain people around, Minato with his students, Hiruzen with Danzo (because Danzo was the advisor and I most likely am going to give him a beating) Iruka and the hyuga leader Hiashi , Kakashi at the time was busy, Finally Madara with Hashirama and Tobirama.

But there was a secret about this spell, it would take them to the true god of Shinobi, The sage of the six paths.