The character business market in Japan was valued at 2.52 trillion Japanese yen as of fiscal year 2020. As the third-largest economy with a 5 trillion usd GDP, Japan is defintely a huge piece of cake in the APAC market. As a well developed country, Japan top the rank in average salary and consuming power among east asian area. Unlike China and Korea, you will be more fmailiar with the marketing platforms in Japan such as Google and twitter. Japanese market might be a good starter among Asian countries but you might have to pay attention to user expereince and localization strategy as making your brnad Japanese friendly is pretty important.