This record tracks a ransomware attack claimed by the
AiLock group against
Yaomasa. It collects the publicly disclosed attack details — sector, location and
timeline — as published on the operator's leak site and indexed by Breach House.
Window Zero
EXPOSURE GAP
Window Zero is the time the breach stayed in the open before
anyone said so — the gap between when the attack was first discovered
on the operator's leak site (t1) and when it was publicly disclosed (t2).
The wider this window, the longer victims, staff and customers were exposed with no warning.
-50days
t1 · Published
t2 · Disclosed
Business Category
Manufacturing / Engineering
Published
August 13, 2026
Disclosed / Notified
Jun 24, 2026
Attack Summary
Yaomasa is a Japanese supermarket chain founded in 1919 that offers fresh foods, general groceries, and daily necessities, while also operating TSUTAYA and BOOKOFF franchise stores as part of its cultural division.
Leak Screenshots
SAMPLE
Proof-of-breach screenshots the operator posted from the stolen data. Previews are
redacted and locked — the originals are available on HaveIBeenRansom.
Dark Web Exposure
Findings for yaomasa.com
— indexed by HaveIBeenRansom.
0
found in Infostealer logs
10
found in Traditional breaches
0
found in Ransomware leaks
Cit0day [cit0day.in] breaches.csv
LKnet reserve chat · breach
••• emails
VerificationsIO_BF.7z.011
Kedr | Forum · breach
••• emails
2844Breaches_BF.7z
B F R e p o V 3 F i l e s · breach
••• emails
Collection_RF 1300 DB.zip
DBs Backup · breach
••• emails
Collection#3.zip
DBs w MTDT · breach
••• emails
ANTIPUBLIC #1.tar.zip.001
DBs Backup · breach
••• emails
Leak volumes are locked
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Legal Disclaimer:
This ransomware victim record reflects information published on the operator's leak site.
Breach.house does not acquire, download, host, access or redistribute unlawfully obtained data. It indexes only publicly visible information posted by ransomware, breach and infostealer operators and open web sources, without accessing the underlying stolen content. The service supports public awareness, legitimate research and cyber-resilience.