Information from Digital Agency, Government of Japan: "Visit Japan Web"

Digital Agency, Government of Japan, deploys an online service, called "Visit Japan Web", that allows you to register the necessary information for Immigration and Custom Declaration in advance, and present the QR code with your passport at the check points of Immigration and Customs to ensure a smooth entry process.

You can access the form Digital Agency, Government of Japan prior to your arrival in Japan.

Please note that the existing paper version of the Customs Declaration Form can still be used.
For details, please see the Japan Customs website (Declaration of Accompanied Articles and Unaccompanied Articles)

Furthermore, when passing through customs at the airport, passengers can now use smartphone payment apps and credit cards to pay any customs duties, consumption taxes, etc. on their personal belongings, etc.
For details, please see the Japan Customs website (Cashless payments of customs duties and taxes by passengers)