Photo/Illutration A copy machine at a convenience store that issues copies of residency certificates (Asahi Shimbun file photo)

Four people in Yokohama who used a machine on March 27 to get their residency certificates instead received ones belonging to someone else due to an overload in the system, according to city officials. 

The mishap occurred at a convenience store using a machine there to obtain their certificates of residence using their My Number Card.

Five such resident certificates were issued by mistake that day, according to the Yokohama city government and Fujitsu Japan Ltd., a company that provides the city with the certificate-issuing service.

The company said too many people used the system at the same time because it was the end of the fiscal year, which overloaded the system.

The trouble did not originate from the national My Number Card system itself, telecommunications minister Takeaki Matsumoto said at a news conference on March 31.

“Still, I have taken seriously the fact that a certificate for somebody else was issued,” he said.

Taro Kono, the minister for digital transformation, apologized at the news conference for the mistake.

“Safety in a system that handles personal information is extremely important," Kono said, urging operators to take careful steps to better develop and operate such systems.

Some local governments that use the same Fujitsu service took precautions and temporarily halted issuing certificates at convenience stores from March 28.

About 30 organizations use the same Fujitsu system, according to the ministry.

As of the morning of March 31, no mistake had been reported other than the five cases in Yokohama.

(This article was compiled from reports by Yoshikatsu Nakajima, Yasuyuki Onaya, Kaho Matsuda, Yuka Yokokawa and Seiko Sadakuni.)