Kerevi, 26, will join Suntory after the World Cup in Japan but with only 25 test caps he will be ineligible for selection for the national side.
Australia only select domestically-contracted players unless they have played 60 tests, an exemption they introduced in 2015 to allow coach Michael Cheika to pick overseas-based players like Matt Giteau for the Rugby World Cup that year.
Kerevi said moving to Japan would allow him to financially support his family and spend time with his younger brother, who also plays rugby there.
"It was a tough decision but one where I had to think about myself and my family, especially my little brother," Kerevi told reporters.
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"The money is awesome, comforting, a safety net, but I've missed a lot of my little bro's life.
"I'd say he's the biggest factor."
While the Wallabies have lost Kerevi for the foreseeable future, his centre partner Tevita Kuridrani confirmed he had signed a one-year contract extension with Super Rugby's Brumbies, who face the Reds on Saturday in Canberra.
Kuridrani, who scored a try in the 2015 Rugby World Cup final against the All Blacks, missed all of the Wallabies tests last season through injury but has been in strong form this year.
"I'm pleased he's staying in Canberra with the Brumbies after the World Cup," Cheika said in a media statement.
"He got the chance to get a full preparation this year and its showing.
"I know he's very hungry to earn a test jersey again this season so I am looking forward to him being at his best in 2019."
(Reporting by Greg Stutchbury in Wellington; Editing by Peter Rutherford)
