IT IS THE TRUE WORLD TOURNAMENT SAGA IT IS WHERE YOU PLAY IN THE DRAGON BALL SAGA AND YOU ARE LIKE KID GOKU AND MASTER ROSHI AND GENERAL TOA
Actually if you listen to the prolouge, it says that "time and space will be broken for these incredible fight" or something. And if you listen to the characters they give you clues that their actually suppose to be the present day fighters. Like piccolo saying "goku in his kid form, weird but I would love ot fight him again." Or master roshi saying " I havent seen you in long time as a kid, goku"