This is not a direct reply to your question, but: look to the
SCA for how this works in real life. The combat is a legitimate martial art -- and involves wearing a suit of armor. Somebody had to make that suit of armor. The members fight with relatively safe weapons. (Think of a stickball bat, then imagine you have armor on.) They also carry real weapons, have contests with archery and crossbows,
et cetera. Somebody had to make those weapons. The King is chosen in trial by combat; somebody had to make his crown and sew his robes. (There have also been a few Queens by right of arms. They need regalia too.) And after the trial by combat, everybody celebrates by sitting down to a proper Medieval feast.
These are all arts and crafts practiced in support of a martial art. It's the same in Nerima, I imagine. Their gi didn't grow on a tree. Their bokken grew on a tree, but it took a fair bit of work to separate it from the tree and get it ready to use. Somebody has to make and maintain the dojo. (That's a tough job in Nerima.)
As I said -- not what you asked for, but worth considering.