Super Dragon Ball Heroes: Universe Mission summary:

Super Dragon Ball Heroes: Universe Mission is a spin-off manga and the sequel to Super Dragon Ball Heroes: Dark Demon Realm Mission!.The plot involves the mysterious Fu, who after kidnapping Future Trunks, lures Goku and Vegeta to the Prison Planet, an experimental area which Fu created and has filled with strong warriors from different planets and eras in order to force them into a game where they must collect the seven Dragon Balls if they wish to escape.