The 29-year-old has begun a three-year deal with the Toshiba Brave Lupus in Japan’s League One.
The New Zealand Herald understands the deal is in the region of $2 million per season.
He is joined at the club by Highlanders and All Blacks flanker Shannon Frizell and former Crusaders centre/wing Seta Tamanivalu, while the side is coached by former Crusaders captain Todd Blackadder.
Mo’unga could, potentially, return to New Zealand in mid-2026 and put himself in the frame for the World Cup in Australia the following year by first playing the provincial season. At that point, he will be 32.
However, the multiple Super Rugby champion says he can imagine playing in Japan “until I retire”.
“I’m focused on the present, I just want to give all I can to Toshiba,” he told reporters this week.
“I really can see myself playing here as long as I can until I retire.”
Mo’unga started in this year's Rugby World Cup final 12-11 defeat to South Africa, his 56th test for the All Blacks.
He sits fourth on the all-time list for most points scored for the All Blacks with 466.
Fellow departed All Blacks now readying for a season in Japan include former Highlander Aaron Smith, Beauden Barrett and Brodie Retallick, while captain Sam Cane is taking a sabbatical and skipping Super Rugby Pacific to play for Suntory.
“I don’t like using the term ‘sabbatical’,” Mo’unga said.
“This isn’t a rest for me, it’s not a one-year thing. I’m fully involved and fully committed.”
Toshiba Brave Lupus finished fifth last season, just outside the playoffs.
“Every year for a long number of years, it’s been the same, same, same,” Mo'unga said.
“This is an experience for myself to test my abilities in a different environment.”
The first five-eighth told the Herald last year he was ultimately swayed by the chance to set his family, which includes young daughter Billie and son Marley, up for life.
“It’s a touchy thing when people are going overseas but you can’t hide away from the fact it’s life-changing for me and my family,” Mo’unga said.
“My job as a father and a husband is to provide for my family and put them first in decisions. That’s basically what I’m doing.
“I’ve got a short window to play rugby so it’s taking advantage of that. Japan is a really good fit for me and my family and the age my kids are at. We’re excited to indulge in the culture.”