When the baseball season kicked off in Japan this spring, fans of the Tohoku Rakuten Golden Eagles were faced with an inconvenience they'd never encountered before: The food and drink stalls did not accept cash.

The team's owner, internet commerce firm Rakuten Inc., was trying to promote its QR code mobile payment system. But the marketing ploy quickly turned out to be much more than that.

In April and May, food, beverage and merchandise sales at the Eagles stadium in Sendai jumped 20 percent from the same period in 2018, partly because taking cash out of the equation changed spending habits.