Joseph will take control of Japan at the conclusion of the Super Rugby season, where he is currently in charge of the defending champion Otago Highlanders.
Japan have beaten Georgia in three of the four tests they have played, winning the last meeting in Sept. 2015, 13-10.
Wales have beaten the Brave Blossoms in eight of their nine encounters, although Japan won the most recent contest in Tokyo, 23-8.
Fiji have won 13-of-16 games against Japan, including a thrilling 35-31 victory during the 2007 World Cup in France.
Japan, currently under the stewardship of interim coach Mark Hammett, play Scotland in Toyota City, Aichi Prefecture on Saturday and at Tokyo's Ajinomoto Stadium on June 25.
(Reporting by Simon Jennings in Bengaluru; Editing by John O'Brien)
