We analyze Japanese household payment behavior and estimate the welfaremaximizing circulation of a central bank digital currency (CBDC) using a dynamic stochastic general equilibrium (DSGE) model. Based on a nationwide survey of 8,000 individuals conducted by Nomura Research Institute in 2024, we find that households would convert approximately 15.6% of their cash and 12.7% of their deposits into CBDC, suggesting a digital yen would partially substitute for existing means of payment. Calibrating the model with Japanese macroeconomic and financial data and incorporating household liquidity preferences derived from the survey, we find that when the CBDC interest rate is set to zero, the optimal circulation of CBDC amounts to 92 % of quarterly GDP, exceeding the euro area benchmark of 64 % (Burlon et al., 2024). The larger optimal quantity of CBDC in Japan may reflect not only differences in household liquidity preferences, but also structural characteristics of its financial system, including a larger central bank balance sheet and a higher ratio of corporate lending to GDP.