J PREP: Saito Juku staff email account accessed

At J Institute Inc. (renamed J PREP Inc. in March 2026), a third party accessed one staff member's internal system account from about 20:55 on 4 July to 16:30 on 5 July 2024, and about 20,000 sent and received emails may have been stolen. Suspicious phishing emails were sent from the account on 5 July, and it was locked. Data includes names, gender, age, grade, school, email addresses and some grades of some J PREP Saito Juku students, plus names and email addresses of people who exchanged email with the staff member.