(Tokyo) The automated cash register at Hiroshi Nishitani’s ramen restaurant in Tokyo has been reliable for a decade. Customers give her money and she prints their order while Hiroshi Nishitani prepares fresh noodles in the kitchen. The dishes are served in a few minutes, once the customer has transmitted their order to the couple of cooks at the counter.

But this machine’s days are numbered. Japan is set to introduce a new series of banknotes this summer, something it does about every 20 years to thwart counterfeiters. The machine, already too old to accept recent coins, will not accept new notes, Nishitani said.

“There is nothing wrong with the machine,” he assured, expressing frustration over the need to purchase an expensive new device compatible with the new banknotes.

Across Japan, restaurants, cafeterias, public baths and other businesses are facing the same situation. The country has 4.1 million vending machines, according to Nikkei Compass, an industry database. Many of these will be obsolete when the new 1,000, 5,000 and 10,000 yen notes, featuring holographic technology, go into circulation in July.

In Japan, where the workforce is shrinking, machines are reducing the number of cashiers and waiters. Ramen shops, which serve one of the favorite and most affordable meals of Japan’s working class, are among those most reliant on these machines.

Ramen, wheat noodles in a richly flavored broth, became an integral part of Japanese cuisine after being popularized in the 1980s as the country’s economy took off. Restaurants mushroomed as people demanded this quick, filling meal and chefs experimented with new ingredients. Many chefs today dedicate their lives to perfecting this dish. Mr. Nishitani, 42, started making ramen when he was 17.

Noodles are a staple food for construction and factory workers, salarymen and students looking for an inexpensive meal. Many ramen shops are clustered around train stations, to meet the needs of commuters.

On a Tuesday afternoon, students from a nearby university came to have a late dinner at Mr. Nishitani’s nine-seat store, Goumen Maruko.

He and his three employees sell about 100 dishes a day. Each dish costs less than 1,000 yen, or about $9. The most popular dish is a $7 Jiro bowl: noodles with a mountain of vegetables and chunks of pork fat dipped in a steaming pork and chicken broth. The more expensive dishes, which come in larger portions, cost around $8.50.

To cover the cost of upgrading or replacing machines, some municipalities offer grants, but most of the cost falls on the store owners. A new machine can cost 2 million yen, or about $17,500, said Masahiro Kawamura, sales manager at Elcom, a Tokyo company that sells ticket vending machines.

Yoshihiro Serizawa, who runs a soba shop in Tokyo, said he spent about $26,000 on his new machine, which also accepts card payments, representing a “huge financial burden.” That sum equates to more than 6,000 orders of its most popular dish: soba with mixed vegetables and tempura seafood, which costs just over $4.

The new banknotes increase the pressure on small Japanese businesses. Recently, inflation has accelerated after remaining low for years, and the country has entered a recession.

Rising flour and electricity prices have increased expenses for ramen shops in particular. According to analysts at Tokyo Shoko Research, 45 ramen restaurants filed for bankruptcy last year, the highest number since 2009. With customers unaccustomed to rising prices, companies are struggling to raise them.

Among ramen chefs, the widely accepted limit for a bowl of ramen is known as the “1000 yen wall.”

“I really don’t want to raise the price any further,” Mr. Nishitani said.

When Japan released its last series of banknotes in 2004, modifying the vending machines and issuing 10 billion new banknotes cost hundreds of millions of dollars. Demand was so strong that a manufacturer near Osaka, called Glory, saw its net income triple, according to an annual report.

The transition to new machines could take years. By summer 2023, only about 30% of beverage vending machines could accept the 500 yen coins introduced in 2021, according to the Sankei Shimbun, a Japanese newspaper.

Mr. Nishitani’s vending machine also doesn’t work with these coins. His Tokyo district is offering a subsidy of up to $2,600 for the purchase of new dispensers, a municipal official said. Mr. Nishitani scoffed at the suggestion that it was nearly enough.

Two months before the new tickets are issued, he still has not ordered a new machine. It recently began accepting payments through a credit card reader for the first time. But this came with additional administrative costs and additional work.

“I can’t get used to it at all,” he said.