On April 1, 2022, the Japanese amicus brief system was enacted. In the system, the court may seek from the general public submission of written opinions regarding issues in the case such as the application of the Patent Act. The overview of the system is explained in the Japan IP High Court’s following homepage in English.
https://www.ip.courts.go.jp/eng/Guidelines_for_Proceedings/vcmsFolder_1618/vcms_1618.html
On September 30, 2022, the Japan IP High Court announced to utilize the amicus brief system for the first time (Case No. 2022 (Ne) 10046). In the case, the court publicly called for third parties’ opinions regarding the issues in the case by November 30, 2022. The guideline on the call for opinions in English is as follows:
https://www.ip.courts.go.jp/eng/vc-files/eng/2022/boshuuyoukou_en.pdf