Getting a missed parcel redelivered in Japan, forwarding your post when you move, what customs does to a package from abroad, and what happens to your mail when you leave.
This page does not yet list the offices, forms, costs or step-by-step procedures for it beyond what is above. The Immigration Services Agency publishes the Daily Life Support Portal, which covers this ground officially, free, in 19 languages, and is written by the agency that administers the procedures.