Joseph was introduced as the coach of the Cherry Blossoms at a media conference in Tokyo late on Monday.
The Japan Times reported Joseph said he was willing to take some losses for his new team so long as it won the ones which mattered at the 2019 World Cup, which is being hosted by Japan.
Joseph signed to coach Japan in January but coached the Highlanders to the Super rugby semifinals, leaving the franchise after six years in charge - the highlight being the title win in 2015.
Joseph said at the press conference he was excited about coming to Japan once again. The former loose forward had played in Japan from 1995 to 2002 for the Sanix Blues club and played for Japan at the World Cup in 1999.
He said there was a lot of hard work to be done, but he was looking forward to it.
He arrived in Japan last week and told media he had a basic knowledge of the team.
Over the next two weeks he was hoping to meet all of the players and Top League coaches and start building for some tough games coming up.
Joseph will coach his first test when Japan takes on Argentina in Tokyo on November 5. It will then travel to Europe to take on Georgia, Wales and Fiji.