Which is the competent authority for utility model patent applications in Japan?

The JPO conducts formality examination only for utility model patent applications.

Inventors have a novelty grace period of 12 months after disclosure (including sale).

yes. Multiple designs may be included in one design application.

• Grant fee: The applicant shall pay the granted fee within 30 days after receiving the granted notice.
• Annuity: The annual fee for the first to third years must be paid together with the application fee when the patent application is filed, and the annual fee will be paid year by year from the fourth year, and the payment period corresponds to the granted date. 200% of the year's annual fee paid within the month is a late fee.

Japan Patent Office

English: Japan Patent Office, abbreviation: JPO

Website: Japan Patent Office (jpo.go.jp)

Japanese Invention Patent Search: Japan Platform for Patent Information｜J-PlatPat [JPP] (inpit.go.jp)

10 years

• Inventions under the via Paris Convention : 12 months from the earliest priority date.
• via Nationalization of PCT inventions: 30 months from the earliest priority date.

yes

25 years

• via Paris Convention : 12 months from earliest priority date.
• via Nationalization of PCT : 30 months from the earliest priority date.