If you have lost property
If you have lost property, go to the nearest police station or Koban (Police Box) to check if it has been found.
If you lose something while riding public transport, try the following:

Train: Ask the railway station staff. (If you know the name of the destination of the train you were riding, it may be easier to find your lost property.)
Bus:  Ask at one of the bus company’s offices.
Taxi:  Ask at the taxi company’s office.


If you find lost property
Take any found lost property to the nearest police station or Koban (Police Box) as soon as possible. If you find it on a train or in a department store, take it to a railway station employee or to the lost property department of the store. In either case, be sure to obtain a Shutoku-butsu Azukari-sho (Deposit of Lost Property Certificate/Slip).


Note 1 　For details, ask a person who understands Japanese to enquire for you at a police station or Koban (Police Box) near you.

This information is from the CLAIR website. The Council of Local Authorities for International Relations (CLAIR) was established in July 1988 in response to rising concerns about local level internationalization in Japan.