And the 38-year-old has taken over as head coach of Harbour. He had a brief stint with the club last year as the backs coach and is trying out the role to see if it is something he might like to pursue further.
"Being a coach is a little bit different, especially club rugby," Nicholas said.
"There are a lot of things you don't have to deal with as a professional player in Japan, like getting guys to turn up to training and having enough balls at practice - just the little stuff like that which you take for granted.
"It is real grassroots. It is a big change."
But while there are some frustrations, there are also rewards as well.
"I really enjoy it. There is a really good group down there.
"There is a lot of Pacific Island boys down there I can relate to and my brother [Ngana Nicholas] is playing there."
Nicholas has property interests in the Cook Islands and in New Zealand but is keen to see where coaching will take him.
"At this stage I'm just sort of getting a feel for it and seeing if it is something I want to do.
"I wanted to have some sort of focus when I came back. I didn't want to get straight into a job or anything like that.
"The opportunity came up at Harbour and I thought why not - it will give me something to structure my week around and get a feel for coaching.
"The only thing about coaching as a career is it is quite a nomadic lifestyle and can be very hard to stay in one city. I'm not sure I actually want that for me and my family."
His wife, Sara Laban (41), grew up in Dunedin and Nicholas spent eight years in the city while at University and playing for the Highlanders.
Laban returned to Dunedin during Nicholas' final season in Japan and set up camp. The couple have two children - son Marama (12) and daughter Anya (4) - and live in Maori Hill.
"She started to put some roots down and I was happy to come back here. She spent 13 years following me around the world while I was doing what I wanted to do, so it was the least I could do.
"But I have heaps of mates here and it is a nice little city.
"We've fallen back into things here and New Zealand affords a pretty good lifestyle."
Nicholas played 24 games for the Highlanders between 2002 and 2004. The hard-running centre scored seven tries but left for Japan to play for Suntory Sungoliath in 2005.
He had 11 years at the club before joining Mitsubishi Sagamihara Dyna Boars for his last two seasons.
He also played 38 games for Japan between 2008 and 2012, so he has a lot of experience.
Otago coach Ben Herring is keen to tap into that knowledge and has called Nicholas in to help with some of the promising Otago players. But for now he is happy to learn the ropes slowly and help Harbour win that elusive senior banner.
That would be a great start to his coaching career.