Vunivalu was 18 and a member of the Blues development squad in Auckland when he signed a contract with the Storm in the NRL. Between 2016-20 he played 111 times for the Storm and shared in two NRL grand final wins.
He was also a prolific try-scorer for Fiji's rugby league team.
But in 2021, he returned to rugby with the Reds, and coach Dave Rennie had him in the Wallabies' training camps in November 2020.
Troubled by injuries in 2021, he was included in the Wallabies squad to prepare for their July series with England after a stellar season with the Reds.
The try-scoring wing praised Thorn's contribution to his readjustment to rugby.
"He's been really helpful since I got to the Reds," Vunivalu told rugby.com.au.
"He knows best how the game is, and he's helped me so much, and I'm looking forward to spending another year with him.
"He's been [in a similar] position. He knew the first couple of games would be rusty and that I was a bit nervous knowing I had my second surgery [on his hamstring].
"He was always supportive and always looking after me," he said.
Although transferring to league, Vunivalu said he always intended to return to rugby.
"I didn't know I was ending up in rugby league leaving school. When I was [at the Storm] with Nelson [Asofa-Solomona] and we talked about spending a couple of years in rugby league and then head back to union when we were 24-25, and it happened for me," he said.
That was because he appreciated rugby's contestable nature.
"Everything is contestable, and you have licence to kick, whereas you can't kick when you catch it at the back and you have to run straight into a wall of defence [in league]," he said.
Rugby offered the freedom to move off his wing and look for work. He said he had been working on his kicking game with five-eighths James O'Connor.