Dagg confirmed he will join the Canon Eagles when his Super Rugby duties finish and return to New Zealand in December.
The 66-Test veteran hasn't played for New Zealand since last September, having been sidelined for long periods by a chronic knee problem.
He has made just four appearances for the Crusaders, with a return to the field in May cut short when hit in a high tackle by Brumbies winger Chance Peni.
The 30-year-old says his Japan stint doesn't mark the permanent end of his Test career.
