Players can switch their international allegiance by participating in Olympic sevens qualifying events, provided they have a passport for a second country and have completed a stand down period of at least three three years.
Tamanivalu moved to New Zealand as a teenager to attend Saint Kentigern College, before going on to represent the Chiefs and Crusaders in Super Rugby.
Tamanivalu played three tests for the All Blacks in 2016 but said he would love the chance to represent his Fijian heritage.
"I think I still have a lot to offer for the Fiji team as well if I'm (selected). I'm still young, I'm only 29, and I think I can still play test rugby," he said.
"It was in the back of my mind to play for Fiji (when I moved overseas). I talked to a few of the boys as well from the team to see what they think and a few of the boys in their team are really supportive as well."
The Lautoka-born midfielder was first called into the All Blacks squad in 2015, where he rubbed shoulders with the likes of Ma'a Nonu, Conrad Smith and Sonny Bill Williams, but was not selected for that year's World Cup triumph in the UK. He finally got his chance the following year, playing three tests off the bench against Wales and Australia, and said it was worth the wait.
"I can't explain the feeling eh - it was unreal. I think it would have to be the best thing I've achieved in my career to be an All Black and I have no regret, to be honest, to represent New Zealand," he said.
"I was young, I was excited - what can you do when the best team in the world approached you and say come and play? I was excited, my family was fully supportive and my teammates and all my mates as well."
But Tamanivalu didn't always want to be an All Black.
"In Fiji we're into the Wallabies more, maybe because there was more Fijian boys playing for the Wallabies back in the past. My dad and my family they are all Wallabies supporters but things got changed really quick when I moved to New Zealand."
The man from the Yasawa-i-rara village said it also meant a lot to people back in Fiji to see one of their own playing for the world champions.
"Everyone is supporting the All Blacks and everyone in the village because maybe I'm probably the first one. It's not common in Fiji for someone to play for the All Blacks, just a few of us.
"Not just my family because my old village was really proud and everytime I come back home they put up a big feed just to say thank you for representing the village."
After two years in Bordeaux, the Tamanivalu's moved to Tokyo at the end of last year, with Seta joining Toshiba Brave Lupus in the Japan Top League.
Rugby commitments and the small matter of a global pandemic meant he had not been able to visit his parents in Fiji since December 2018, but the family -including wife Brittany and son Ricky (who turns three in a couple of weeks and will become a big brother in July) - did their best to keep in touch via social media, he said.
"We have a group chat there and sometimes we call each other because we're trying to keep that connection with my son because they're missing out a lot of stuff with my son - the same as my wife Brittany's family (in New Zealand), so we're trying to keep in touch every day. They ring every day with Skype and speak Fijian to him and stuff like that."
The former Crusaders star is among familiar faces at his new club Toshiba Brave Lupus, with Matt Todd, Tim Bateman and Jack Stratton all former teammates from his time in Christchurch.