Tremain, 19, had three club games for his University club side in Wellington to prove he was ready for the Oceania Championship where the Baby Blacks won all three of their matches against Tonga, Fiji and Australia. Tremain is playing for University while studying Commerce at Victoria University where he is majoring in Commercial Law and Economics.
"Hopefully I play well enough in France to earn a spot in the Magpies Mitre 10 Cup squad," Tremain said.
At the Oceania Championship on the Gold Coast, Tremain had 20 minutes as a substitute against Tonga, the full game against Fiji and 12 minutes off the pine against Australia.
"It was a pretty special moment to pull on the black jersey for the first time over there. By the end of the tournament, 10 family members were over there and that added to it," the grandson of All Black and Magpies great, the late Kel Tremain, explained.
"Obviously now I'm in the World Championship side, the aim is to push for a starting spot. That will be a tough challenge with Tom going so well but you never say never," Tremain said referring to captain Tom Christie of Canterbury who along with Auckland winger Caleb Clarke are returning from last year's world title-winning Baby Blacks team.
"Coming in a little bit late, it took me a while to get clarity around game plans in Aussie. But Craig [Philpott] has told me to keep playing good rugby and push for starting spots."
After Japan, the Baby Blacks will meet Wales and Australia in pool play. Tremain believed the Aussies will come back as a different side to the one the New Zealanders beat 43-28 on the Gold Coast.
"They certainly weren't down on physicality."
A product of Eskdale and Hereworth schools before attending NBHS, Tremain, had two years in the Hastings East Ross Shield team. He has also represented Hawke's Bay at under-16 and under-19 levels.
Hastings Boys' High School old boy Flanders is one of eight players in the Baby Blacks squad who will be eligible for next year's team. Considering his dominant role in HBHS's march to the national Top Four title last year, his man-of-the-match display for the New Zealand Secondary Schools team in their 34-11 win against their Aussie counterparts last October and outstanding displays for the Hurricanes under-20s earlier this year, Flanders was always on track to get the nod from Philpott and co.
Magpies prop Tim Farrell was one of five players not considered for the trip to France because of injury. Farrell missed the bulk of last year's world championship through injury.
Former Magpies head coach Philpott said it was a tough job selecting the squad of 28.
"We have been impressed with the quality of players that have been with us throughout our camps and at the Oceania Championships, which meant it wasn't easy to narrow this group down."
Twelve of the 28 including Sullivan have played at Mitre 10 Cup level and 27 of the squad have been involved in an Oceania Championship campaign.