Manu's rise into the Kiwis comes after he enjoyed a breakout club season and played a starring role for the Roosters throughout the playoffs and in last month's grand final win over Melbourne.
His hard-earned success comes after he overcame some self-doubts and a below-par 2017 season which left him fearing he would spend the year stuck in reserve grade.
"I didn't have a great season last year and at the start of this season I didn't even know if I'd make the starting 13 for the Roosters," he said.
"To get a premiership ring and then be selected for the Kiwis the next day was something I never thought would happen.
"It's obviously a dream come true. After the GF I was over the moon but now that I'm here I know that I've got to do a job for the Kiwis.
"I'm really looking forward to Saturday and my main focus is here and on getting a couple more wins."
Kiwis coach Michael Maguire has been impressed with Manu's maturity throughout the build-up and is confident he'll handle the challenge of containing Mitchell.
Manu was the quiet-achiever in the Roosters backline but declared himself a representative star in the making when he kept Greg Inglis quiet in the semi-final win over South Sydney, before crossing for a first-half try in the decider against the Storm.
"He's a really mature young man. He's had a great experience with what he's gone through this year and he's shown he can step up as he has done every time he's been asked," said Maguire. "This is another opportunity now for him to show what he's capable of at international level."
Manu won't lack for support with "nearly all of Tokoroa" making the trip up for the occasion.
"It's awesome to be here in New Zealand and to play here," he said.
"I'm really happy to play here in front of my family. It should be good for us and New Zealand rugby league, and all the fans."
