I couldn't start the game, I could select a character for one of the slots, left and right change weapon and O/Z make him 'ready' but couldn't figure out how to get further

The game cannot start unless there are at least 2 players, and apparently the controller assigned to player 1 and 2 seem to change. Ultimately, however many players need to join, then all ready up with player 1 doing this last <3