Three big banks, and other 27 company from the private sector just started the digital yen operation, to testing the possibilities. There are not much clear details about it, but it will be a hard ride. Japan is cash-friendly, the settlements in the country still made with cash, in 80%, compared to 55% in USA, and 30% in China.
And next to the technical issues and challenges, there is at least one philosophical roadblock. The goverment does not want to people withdraw their money from bank deposits en masse. It could be harmful for banks. But does not want to start a payment system (aka CBDC), what wont be used widely.