The 29-year-old abandoned a flourishing rugby league career at the end of 2021 in a bid to land a place in the New Zealand squad for next year's World Cup in France.
Despite some in New Zealand feeling he has not been used enough by the All Blacks this season, the former NRL star is happy with his progress, which takes another step on Saturday when he suits up in Tokyo for his first start with the national team.
"This is another massive chapter in my learnings for this year," the fleet-footed centre told Stuff Media.
"I've made the crossover from rugby league, and the ultimate dream is to be part of that World Cup squad next year.
"It was just a bonus to be called up this year, and I'm stoked to be getting a Test match start.
"I've got to enjoy every moment and opportunity I can."
But for his decision to switch codes, Tuivasa-Sheck would be lining up for his country in a Rugby League World Cup match against Ireland in Leeds later on Friday.
Tuivasa-Sheck said being parted from his family during the COVID-19 pandemic when the New Zealand Warriors relocated to Australia, had been a key factor in deciding to give the 15-man game a go.
"I made the decision I was going to risk all or nothing and try my luck at rugby union," he said.
"I'm just so happy to line up with a World Cup that's there to be chased.
"I back myself to chase it and then return back home to be with my family."
Tuivasa-Sheck will win his third cap against the Brave Blossoms at Tokyo's National Stadium on Saturday in a makeshift centre partnership alongside Braydon Ennor.
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