Barrett, 29, signed a four-year deal with New Zealand Rugby (NZR) and the Blues in 2019, but will head to Japan in 2021 before returning for the international season.

The star playmaker will play under Kiwi coach Milton Haig, while England head coach Eddie Jones is a consultant for Suntory Sungoliath.

"For me it made sense to go next year and then have two years back with the Blues and hopefully the All Blacks in the lead up to the Rugby World Cup," Barrett said.

"My wife and I are excited to head to Japan next year. It is an appealing place for a young family and comparatively safe in health terms.

"The Investec Super Rugby Aotearoa competition has been an amazing experience. It's been brutal and demanding which is what you expect when New Zealand teams play each other.

"I'm loving every minute of it and having such big crowds turning out has been fantastic. I am loving the move to the Blues and we still have a job to do this season. It is an excellent environment with great coaching and an awesome bunch of dedicated players.

"While the excitement about heading to Japan will build closer to the time, I'll also be looking forward to being back later in 2021 and then into the 2022 Blues season."

All Blacks Brodie Retallick and Sam Whitelock have had similar agreements to play in Japan this year.

Blues head coach Leon MacDonald said he was planning for next year without Barrett.

"Our focus is fully on the current campaign but we have plans for next year without Beaudy," he said.

"He will be a big loss but that is countered with what he is doing on and off the field this year, and that we get him for two more years.

"We have Otere Black playing terrific rugby, and Harry Plummer who has been coming off the bench, while we will have Stephen Perofeta back next season from injury."