If service has not been made by adhering to the opponent, etc., final service by publication in the Official Gazette and Patent Gazette, posting in a designated posting area in the JPO office, display on a computer for public inspection in the JPO office, etc., will be made by public notice.

For more information on the introduction of the new system, please see the following link.

Japan Patent Office
Information on Service by Publication (Patent Gazette)
https://www.jpo.go.jp/e/system/laws/koji/index.html