13U with leadoffs, balks, etc.
Runners on first and third and a left-handed pitcher on the mound. Runner on third takes off running, then the runner on first takes off running. Pitcher throws to first base (either a legal pick off or a step off...doesn't matter). First baseman catches the ball and then throws to the catcher. Does the hitter who was in the box have to vacate the box or can he stay in there and the play goes around him (runner slides between hitter's leg or around him, etc)?