Groin Ball is a much more sophisticated testicular game than Roshambo (the brutal ball kicking game where players face each other and take turns to make unguarded kicks into the other's groin until one player gives up. Games are usually extremely short lived.)
This classic Japanese version of Groin Ball is played between two teams of two players. Each team consists of a ball thrower and a target player. The two opposing target players face each other and with their hands they hold one another's shoulders. They also need to keep their feet about shoulder width apart and they need to maintain this stance throughout the game.
The throwing players have a ready supply of tennis balls. They then have to fire these through the open legs of their partner, bouncing onto the ground with the hope of bouncing up and smashing into the groin of the opposing target player. Target players can move around and push each other in order to move them into a vulnerable position but they must maintain the hand shoulder contact. Similarly the ball throwers can move anywhere so as to get a clean aim and as soon as their ball supply has gone they can pick up ones on the floor and keep up their frenetic throwing pace.
What makes the game especially thrilling is that the target players have to keep their feet well apart so that their partner can fire ball through the gap while they may desperately want to close them after receiving the odd strike or two.
The team with the first target player to cry loses.
If you are interested in more ball and groin based fun try Duncan Flann's Groin Ball or Crotch Ball