Having moved to Japan aged 15 as part of an exchange programme with a sister school, Christchurch-born Leitch fell in love with the Land of the Rising Sun, making permanent what was initially a one-year stay.
He continued to play rugby as he furthered his education and, with an ability and physique that set him apart on the local scene, Leitch captained Japan at the 2008 Junior World Championships.
But even as his stature swelled in his adopted homeland, earning a promotion to the Cherry Blossoms under coach John Kirwan, Leitch never imagined his skills would translate to his native country.
"Being in Japan, I didn't really back my ability to play Super Rugby," he said.
"But once I made the Japan team and played in the 2011 World Cup, I must have made a good impression on Wayne Smith."
The then-Chiefs assistant did his due diligence on the bruising loose forward and the Chiefs eventually offered Leitch a wider-training spot in 2013.
But that dream opportunity soon turned into a nightmare, with first a broken arm and then a broken leg preventing Leitch from making the leap into a match-day squad.
"Any other team would have cut me but the Chiefs kept me on and trained me up," he said.
"I would have come over here and just held pads [in training] - that's how keen I was to get here. And while I was over here I had to make the most of the time I had. I just trained hard and I think that left a good impression, which is why I got called back."
That call arrived before the current campaign, with Dave Rennie handing Leitch, now 26, a contract with the full squad. He's since remained fit and retained the No 8 jersey, describing himself earlier in the season akin to a kid at Disneyland.
"I was telling my wife that, while I've been here for a good two months, every day I keep buzzing out about how I'm playing alongside All Blacks.
"You've just got so many high-quality players around you and that's the sort of thing you don't really get in Japan."
Leitch hopes his progress, along with the continuing success of Tanaka at the Highlanders, will help to change that.
He wants more players to follow the pair's lead which, combined with a Japanese expansion team in next year's Super Rugby competition, will only grow the game globally.
"The only way Japanese players are going to get better is if they leave Japan and start playing at a good level," Leitch said. "If there were better pathways for getting into ITM Cup or Super Rugby, a lot more Japanese players would enjoy the opportunity to come over and play."