A physical hard drive that stored names, addresses and consumption data for 10.9 million TEPCO customers was reported missing on June 12, 2026.
The utility discovered the loss during an internal audit and immediately notified the Personal Information Protection Commission. The regulator’s spokesperson said the incident will be examined under the Act on the Protection of Personal Information and warned that any breach could trigger fines.
For customers, the breach means their personal details could be used in phishing or identity‑theft schemes. TEPCO urged users to monitor accounts and promised to enhance its data‑handling procedures.
Missing hardware is not new in the sector, but the scale here—over ten million records—places the incident among the largest data exposures in Japan’s utility industry.