Austin signed a one-year contract with the Yokohama DeNA Baystars on Thursday, Jeff Passan of ESPN.com reports.
Austin declined an Antonio on Friday and elected free agency.
Austin is on the Brewers' Wild Card roster.
Austin hit a pinch-hit three-run homer in Sunday's 8-5 win over the Cubs.
Austin is out of the lineup for Sunday's game against the Cubs.
Austin had his contract selected from Triple-A San Antonio by the Brewers on Sunday, Robert Murray of The Athletic reports.
Austin and the Brewers agreed to terms Tuesday on a minor-league contract, Joel Sherman of the New York Post reports.
Austin opted to become a free agent Friday.
Austin was designated for assignment Friday.
Austin delivered a solo home run in his lone plate appearance Friday against the Brewers.