Japan is bracing for rage against the vending machine

• Japan is a society that's still in love with cash — and vending machines.
• Its decision to start issuing new banknotes has sparked a problem.
• Almost 80% of Japan's vending machines won't be ready to accept the new notes.

In many ways Japan is a country that's firmly embraced technology, yet it still remains attached to good old-fashioned cash.

Shops scattered along the Zelkova-lined avenue of Tokyo's Omotesando and the boutique shopping district of Ginza are no strangers to locals and tourists waving their credit cards. Still, cash remains king in several other locations.

Hole-in-the-wall izakayas (traditional bars), ryokan (traditional inns), and Shinto shrines often accept cash only. Sure, dense urban sprawls like Tokyo or the Kansai region's Osaka are card-friendly, but carrying physical yen is recommended when venturing beyond major cities.

Those carrying cash in Japan anytime soon, though, may want to double-check the type of bills in their wallets.

This week, Japan started issuing new banknotes for the first time in 20 years in an effort to combat counterfeit money. The only problem is that they might not be accepted everywhere.

Take Japan's millions of vending machines. They are big business in Japan, offering everything from hot coffee and beer to wagyu and hot sauce. Though some accept card payments, those that take cash may not accept Japan's new banknotes.

The Japan Vending Machine Manufacturers Association recently said that almost 80% of the country's machines would need upgrades to accept the new notes, per comments reported by Reuters. Parking ticket machines and others would also need a fix.

The issue is that Japan's retro machines aren't designed to process the new notes, which boast high-tech specs incorporated to help determine authenticity.

They include portraits of historic figures as 3D holograms — a world-first, according to the Bank of Japan — designed to rotate when a note is tilted. Getting Japan's aged machines ready for these new notes will now take time, and money.

In April, the Bank of Japan said that despite the growth in cashless payments, it expects "the demand for cash, which can be readily used by anyone, anywhere, and at any time," to "likely continue to play a significant role as a means of payment."

The banknote issues come at a peculiar time. Tourists have been flocking to Japan this year to take advantage of a weak yen, which hit a 38-year low against the US dollar this week.

Travel guides often tell tourists to carry cash. If they're stopping by a vending machine there anytime soon, they may want to check first if their bills will work.