Hi,
In France judicial system, there's a process called "main-courante" : it consists in going to a police station and notifying the police that a certain event has occurred, without actually lodging a complaint. The police will make a note of it in a ledger, and they will NOT investigate.
Have you ever heard of such a thing in Japan? Basically I just want a written document I can use later as a mean to warn someone, but I don't want the J-popo to start asking questions and calling people.