Northampton Saints fly-half James Grayson is to leave Franklin's Gardens to play club rugby in Japan.

Grayson, who has scored 617 points in 92 Saints appearances, will leave Northampton after Sunday's match against Exeter Chiefs.

"Without doubt this was a really difficult decision for me to make," Grayson said.

"Ultimately, this is a decision driven by my desire to play more rugby, more regularly.

"As a professional, all you want is to be able to go out there and play on a Saturday afternoon, so I am making this move to try and further my rugby career - it is an opportunity that I felt like I couldn't really turn down."

Grayson looked set to succeed Dan Biggar as Saints' first-choice 10 when the Wales and Lions legend made his exit to Toulon last season.

But he has remained edged out by Fin Smith's arrival following Worcester Warriors' demise a year ago.

Grayson ended up missing most of last season after suffering a stress fracture in October.

"He's not playing enough minutes," Saints director of rugby Phil Dowson told BBC Radio Northampton.

"It's a chance to go away and play some rugby week in, week out. He's frustrated as he isn't playing enough.

"He has a huge family history here, so it is a big step for him.

"He has been a great team-mate and a great person around the club. One of life's good guys. But it's also a chance to broaden his horizons."