But that smile turns to an impressive poker face when asked where he sees his career heading from here.
Cooper guided the Mitsubishi Dynaboars into the elite tier of Japan Rugby League One at the weekend when they beat the NTT Communications Shining Arcs 33-19 in the second leg of a promotion-relegation clash, having won the opener 33-25.
The former Otago and All Blacks fullback, back in Dunedin for a break and time with family, said it was a job well done, and he was pleased to finish his second stint in Japan as a champion, especially as the Dynaboars had been forced to do it the hard way.
"We got promoted in 2018 but then had a couple of interrupted years with Covid and it all got a bit messy.
"Then they dropped the competition from 16 teams to 12 teams, and it was probably a bit unfair that we ended up missing out, because we were right around that 12th or 13th spot."
The Dynaboars only lost once this season but, under the rather unusual league structure, they faced an elongated qualifying series.
They had to play the Honda Heat and the Kintetsu Liners, and a loss to the latter meant they faced the tricky two-legged clash with the Shining Arcs to earn promotion.
"We spent four months proving we were No 1 and then lost automatic promotion," Cooper said.
"Not often does a first division side lose to a second division side, and we had to do it twice."
Complicating matters was the unavailability of venues because football had taken priority, so the Dynaboars’ "home" game was 500km away, in Osaka.
There was a healthy New Zealand influence on the field at the Dynaboars at the crunch end of the season.
Former Highlanders lock Jackson Hemopo started at No 8, former Otago loose forward Dylan Nel was on the bench, one-season Otago import Nick Ealey was at No 10 (in place of injured former Highlander Colin Slade), Michael Little (son of former All Black Walter) was in the midfield and Matt Vaega (son of former Highlander To’o) started at fullback.
The Arcs had Australian star Israel Folau and 40-year-old former Canterbury lock Luke Thompson, while former Otago hooker Sekonaia Pole scored a try off the bench.
In the division one final, the Saitama Wild Knights beat Suntory Sungoliath 18-12.
Former Blues midfielder Hadleigh Parkes started for the Knights and former Otago hooker Shota Horie was on the bench, while Suntory had its star-studded backline including All Blacks fullback Damian McKenzie, former Highlanders winger Tevita Li and former Wallabies centre Samu Kerevi.
It was the first season of the revamped Japanese league.
"I think, by and large, it was pretty good," Cooper said.
"Obviously Covid interfered a bit, and I think they might look at the playoff system.
"But I do think rugby is heading forward in Japan, and I think this competition has revamped it. It’s a good quality of rugby."
Following his glittering playing career, Cooper has now completed 21 years of coaching across a variety of teams in New Zealand, France and Japan.
He remains passionate about developing and working with players, and guiding a team’s fortunes in the sort of director of rugby role he held at Mitsubishi, and is considering his future options.
"I wanted to finish on this note. I’ve done what I wanted to do in Japan and this is how I wanted my time there to finish.
"I’ve spent a lot of time in Japan, and I’ve spent time in France. So I’m just looking for another opportunity. But at this stage, I don’t believe it will be Japan. I’d like to do something a little bit different."
Pressed if his coaching future lay overseas or back on home shores, Cooper smiled.
"I’m just looking around. I can’t say too much at the moment.
"I need another challenge. I had an amazing time in Japan, and when I jumped on the plane home, I honestly don’t think I’ve ever felt so happy from a rugby point of view.
"It’s challenging. You’re away from home, dealing with all sorts of things, and you’re dealing with high expectations and issues around players.
"I look back and think I’ve done the job I wanted to do, and I look forward to wherever in the world I go to next."
