You travel to the Neptunia universe to start the adventure.

The story will begin from Rebirth: 1

You'll leave for 3 years then return to help.
The second part will Rebirth: 2

You stay as to kinda make up for the 3 years.
The third part will be Rebirth: 3

You wanted to see if there was another dimension and you ended up finding one by accident somehow.
The Fourth Part will be Superdimension Neptunia vs Sega Hard Girls

After all of that you wanted to relax and you did after sometime you end up going through another adventure which will be the last one since your starting to feel adventured out and want to keep the others happy and it will be your Legacy.

The Final Part will be Megadimension Neptunia

Also I'll try to make the story sound just like the game and at times you'll be traveling back to the 7 Deadly Sins universe to get stronger and then you'll come back. It takes place after everything is over. Season 4
I'm trying to fuse the Neptunia Timeline Together. So you can get some kind of Idea in your head.