"It's exciting to put Trael, Andrew, Vilimoni and Tone into the All Blacks Sevens environment in Wellington.
"Our focus when we go into camp next Monday is to bring the new guys up to speed with our structures and the team culture."
Darryl Malcolm was the WHS coach in 2013 when Koroi first made waves at the prestigious Condor Sevens - being chosen in the tournament team and attending a training camp with the NZ Sevens coaching staff.
Malcolm said even then, it was obvious Koroi was destined for the national level.
"Most definitely, the hierarchy had already been drawn on him in 2013.
"He was definitely one of the outstanding attackers and finishers.
"The [WHS] boys will be really stoked to hear that."
While Koroi moved to the noted rugby school in Feilding Ag, he would still return for cameos in Whanganui club and sevens rugby when possible for the likes of Kaierau and Ngamatapouri.
"He's had pretty good people around him that have helped him achieve," said Malcolm.
"That's what happens when you're spotted so early in the piece, and he's done all the right things."
ORFU general manager Richard Kinley told the Otago Daily Times that Koroi was an exceptionally talented footballer and plenty of unions were after him.
Otago had put an attractive package in front of the Kiwi Fijian, which included tertiary study, so he had decided to head south.