The “Related Design System” allows an applicant to file and register two or more similar designs with minor differences, effectively protecting the multiple designs that may have conflicting scope of protection.

It is possible to file an application as a related design in the original filing, or to amend the application to a related design after receiving a double-patenting rejection from the Japan Patent Office.

Further, as each related design is registered individually, if any of the related design registrations in the same family become invalid at a later date, it does not directly affect the other design registrations therein.

• Since the revision of the Design Act in 2020, the period of filing a related design application has been significantly extended to before the date on which 10 years have elapsed from filing date of the “principal design.”
• The expiration date of the design right for a “related design” is the date which has elapsed 25 years from the filing date of the “principal design.”

Source: https://www.jpo.go.jp/resources/report/sonota-info/document/panhu/isho_kaisei_en.pdf

For more information, please refer to our article on the following link : https://www.ondatechno.com/en/news/design/p1161/

Please also refer to the following link.
JPO Guidebook for Overseas Users: https://www.jpo.go.jp/resources/report/sonota-info/document/panhu/design_right_injapan.pdf (JPO website)