The whole trick works with a simple savegame that already has the story through you missed in the story purely garnix. It’s the 3 season episode 1 – 12 of Anime.
First you go into your savegame or the path is the following:
C:\Users\Username\AppData\Local\BANDAI NAMCO Entertainment\My Hero Ones Justice\Saved\SaveGames\SteamID\
here replace the File with the Name “systemdata.sav”
Download the File