The emotion of those moments — and a desire to give back to the Island nation — were key factors in his decision.
"When I think back to my parents' parents, who came over from Tonga and didn't have a lot but did what they could to give us a chance of a better future, I feel it's only right to give back," Fusitu'a told ONE News on Tuesday.
"I've been given this opportunity to do what I love, to play rugby league, because of all they sacrificed."
Last month Fusitu'a — who was born and raised in Auckland — said he was keeping an open mind on his international allegiance and emphasised that he was a proud Kiwi.
But he sees turning out for Mate Ma'a Tonga as a way to move the needle in the Pacific nation, and have a far reaching impact.
"I believe we're able to do something special by playing for Tonga," he told ONE News.
"We have the ability to change the future of rugby league in making it more accessible for not only Tongans, but children all over the Pacific."
Fusitu'a's early call this year showed he has learnt from his errors of last year, when he was still undecided on the morning of the Kiwis team announcement, grappling with the enormity of the decision.
His absence, while not unexpected, is a blow to new coach Michael Maguire.
While the Kiwis aren't short of wingers, Fusitu'a is in career best form.
He is the joint leading try scorer in the NRL (12), is a weapon under the high ball on attack and defence and has added a new physical edge to his game this season.
He's also recorded almost 100 running metres per match and has recorded 10 line breaks.
Mate Ma'a Tonga faces Samoa in Western Sydney's Campbelltown on June 23, as part of the annual Pacific Challenge.