Confirmed
2rinkan confirms app API breach affecting 3,179,454 people
The June 19 final report confirmed personal-information exposure affecting 3,179,454 people. The earlier maximum of 3,455,754 is not retained as an exact total.
Japan: Data Breach Incidents by Country / region
Search incidents by company, country, industry, year and attack method. Review affected data, impact, verification status, company responses and sources.
Investigating
Tokyo Monorail: data of about 3,400 people may have leaked after loss of a desktop PC awaiting disposal
Possible data leak: A desktop PC from Haneda T2, staged for disposal in the T1 warehouse, could not be found during an April 3, 2026 disposal check; disclosed April 23.
Investigating
Mazda Hospital: data of 626 patients may have leaked after imaging contractor cloud misconfiguration
Possible data leak: An imaging contractor mis-set cloud sharing so files were readable by unauthorised parties from early April 2023 to mid-December 2024; disclosed April 23, 2026.
Investigating
Taisei Housy: customer data may have leaked via ielove CLOUD intrusion
After ielove’s CLOUD-intrusion disclosure and an April 20 report saying some Taisei customer data may have leaked, the firm disclosed on April 22.
Investigating
Takahata Town: data of 2,354 people in the paddy-conversion system may have leaked via YCC
Possible data leak: After the April 2, 2026 attack on maintenance contractor YCC, paddy-conversion system data was found on the vendor server; disclosed April 20. Exfiltration not confirmed.
Investigating
Clearth Rent: customer data may have leaked via ielove CLOUD intrusion
Possible data leak: ielove reported unauthorised access and data acquisition on April 5–6, 2026; Clearth’s April 20 notice and May 13 follow-up listed name, email, phone, address and preferences among leaked fields.
Investigating
Oguni Town: 1,369 welfare-medical records may have leaked via YCC ransomware
Possible data leak: After the April 2, 2026 attack on former contractor YCC, April 2019 welfare-medical data was found on the vendor server; disclosed April 17.
Investigating
Nihon Zaitaku: customer data may have leaked via ielove CLOUD intrusion
After receiving ielove’s April 16, 2026 investigation report on the April 5–6 CLOUD intrusion, Nihon Zaitaku disclosed possible customer-data leakage on April 17.
Investigating
Kaneyama Town: town clinic patient data may have leaked via YCC ransomware
Possible data leak: After the April 2, 2026 YCC attack, clinic medical-admin data was found on the vendor server by April 16; disclosed April 17.
Investigating
Rize Clinic: patient LINE data may have leaked after LINE-delivery-system intrusion
After suspicious LINE messages on April 9, 2026, an April 17 update said LINE display names, clinic, campaign interest and some chat history may have leaked. Chart name/phone fields are not stored in that system.
Investigating
Satte City: national-health data of 34,330 people may have leaked via subcontractor YCC
Possible data leak: AGS maintained the high-cost medical-care system and subcontracted to YCC. After YCC’s April 2, 2026 attack, city data held there was found on April 8; first notice April 17 and headcount on May 25.
Investigating
Yamagata Prefecture: about 26,800 entrusted records may have been exposed via YCC ransomware
Possible data leak: After the YCC file-server attack, the prefecture disclosed on April 17 that related data known as of April 16 had been stored on that server. No impact confirmed on live operational systems.
Investigating
Yamagata Kotsu: bus and taxi customer data may have leaked via YCC ransomware
Possible data leak: After the April 2, 2026 YCC attack, build-contract data including ended contracts was found on the vendor server by April 16; disclosed April 17.
Investigating
Nippon Rent-A-Car: car-share member data may have leaked via Nippon Telenet ransomware
Possible data leak: After Nippon Telenet (UPR subcontractor for car-share call centres) was attacked on March 9, 2026, UPR reported on April 13 and Nippon Rent-A-Car disclosed April 17. Rental-car members out of scope.
Investigating
Yamako: 2,398 customer and staff records may have leaked via YCC ransomware
Possible data leak: After the April 2, 2026 YCC attack, core-system data including ended contracts was found on the vendor server by April 17.
Investigating
Shonai Town: library and training-room users may have leaked via YCC ransomware
Possible data leak: After the April 2, 2026 YCC attack, build-time data from the town and its designated manager was found on the hit server by April 17.
Investigating
Jusnet reports possible data leak from employee Chatwork account
Unauthorised access to an employee’s Chatwork account may have exposed names, contacts and business/service-use information. No affected-person or record total was published.
Confirmed
Yokosuka City: data of 145 people and 12 firms leaked via misattached tax FP-consultation list
On April 8, 2026 the tax office emailed the wrong FP-consultation list to another firm; noticed April 15 after one recipient opened then deleted it; disclosed April 16.
Investigating
Yamagata City: staff and resident data may have leaked via contractor YCC ransomware
Possible data leak: After the April 2, 2026 YCC attack, a review through April 15 found city data including ended contracts still on the vendor server; disclosed April 16.
Investigating
Cecile: customer data may have leaked via Nippon Telenet cyber-attack on fax-sending contractor
Fax contractor Nippon Telenet was attacked on March 9, 2026; on April 8 Cecile was told a Feb 24 fax-send backup may have been on the hit server and disclosed April 16.