Fainu was locked in at the Sea Eagles until the end of the year, however, has struggled to break through to first-grade, yet to make his debut for the club.
Despite impressive performances in junior football - where he played alongside the likes of Ben Trbojevic and Josh Schuster - and some solid groundwork in the NSW Cup, he has struggled to make the grade at NRL level in Des Hasler's side.
He missed the opening reserve grade game of the year against the Panthers, while the Blacktown Workers Sea Eagles had a bye in Round 2.
A former New South Wales under-18 star, he scored a try playing for the Junior Blues in 2019 alongside the likes of Bradman Best, Mathew Feagai, Max Feagai, Will Penisini, Tyrell Sloan, Jayden Sullivan, Jackson Topine and Schuster.
According to The Daily Telegraph, Fainu will join the Tigers immediately on a two and a half year deal, which will see him make the move to Michael Maguire's side with a chance to break into first grade.
It would mean he remains at the Tigers until at least the end of the 2024 season.
Stuck behind a long line of players at Manly, including Martin Taupau, Taniela Paseka, Toafofoa Sipley, Josh Aloiai, Ethan Bullemor and Sean Keppie, the move seems to make sense for the youngster, who has three brothers in the Manly system.
More than that, it's a move which makes sense for the Tigers, who need more depth up front. While James Tamou has been recalled to the front row this week, moving Alex Twal back to the bench, their depth beyond the duo and another gun young in Stefano Utoikamanu looks skinny.
Neither club have confirmed the move yet, however, it's understood speculation has been building over the past fortnight.