What if I lose my ID or passport?
Go immediately to any police box or department and file a lost item report. Be sure to make note of the police case number. In order to replace your passport, resident ID card, national health insurance, and so on, you will need to have the police case number available for reference.
If you lose your passport, after you go to the police, also contact your country’s embassy in Tokyo and get instructions about what to do next.