On June 11, 2021, the Japan Patent Office (JPO) announced that following the promulgation of the "Cabinet Order to Amend a Portion of the Cabinet Order Related to the Ministry of Economy, Trade and Industry to Revise Procedures Requiring a Seal, etc." and the "Ministerial Ordinance to Amend a Portion of the Ordinance for Enforcement of the Patent Registration Order, etc." including the Patent Registration Order, a seal will no longer be required for some procedures in documents submitted to the JPO on or after June 12, 2021.
The new stamp will be abolished for 24 types of procedures, including procedural amendment documents accompanying registration of transfer of rights.
Japan Patent Office
https://www.jpo.go.jp/system/process/shutugan/madoguchi/info/oin-minaoshi.html