I Figure 17 ep.3, children compete in a game of Port Ball. Google does not appear to know what it is:

I am surprised that no fan ever recorded it, so here goes.

Teams of four play on a court about the size of a basketball court or somewhat smaller. Where hoops would otherwise be, small pedestals are set. A player is permanently positioned on the pedestal ("a goal"). A half-circle about 2m in radius is marked around the goal. The only other mark is a dividing line which separates the halves of the court.

The objective for a team is to earn points. To deliver the ball to the team's goal is worth 2 points (I have no idea how one can gain 1 point. All matches in the anime ended with an even number of points.). Surprisingly, nobody ever attempts a longer range shot, even though the goal will try to catch a poorly aimed ball, unlike a hoop. Nobody tried throwing high up either, when blocked by an opposing player.

Players cannot carry the ball, so they play on the run them like in basketball. There are many other similarities as well. The question is, why not just play basketball instead? The game seems lively and well conceived, but why? Perhaps it's an issue of equipment and/or basketball rules being too complex for youngsters.