Tetsundo Tanabe was running a kendo dojo in Yokohama when he came up with an idea on how children could avoid the pain of getting smashed over the head with a bamboo sword. His solution was simple: Use softer weapons. [...] Forty-five years after that brainstorm, 400,000 people in 65 countries and regions are playing Tanabe’s invention, called sports “chanbara” (sword fighting), or “spochan” for short.