As I was going through "Consumers: Contact national regulators", I thought it would be better to put the right regulator in the right country instead of putting the regulators in all other countries, and it should be written in the target language (in my case, Japanese) like below:

公正取引委員会
【スマホソフトウェア競争促進法に関する情報提供フォーム】
https://www.jftc.go.jp/soudan/jyohoteikyo/smartphone_software.html

The only way to get in touch with 公正取引委員会 or JFTC regarding the Mobile Software Competition Act is to use the URL above, as the instructions for reporting to them were changed on April 1.