Mo'unga has signed an 18-month deal that will see him play for Canterbury in the 2026 NPC, be available for the All Blacks' northern tour, and the Crusaders and the All Blacks in the 2027 Rugby World Cup year.
Crusaders chief executive Colin Mansbridge said while there had been rumours that Mo'unga may play elsewhere on his return to New Zealand, Christchurch is his home, and it was natural for him to return if he could and it all worked out.
"We're stoked to have him home. This is a place [the Crusaders] where we try to make everybody feel like they belong and it's nice when somebody chooses to come back to the place they belong."
Coach Rob Penney said it was good to have Mo'unga in the environment.
"He's a great Crusader, his legacy speaks for itself [seven Super Rugby championships], and he wants to add another layer to that.
"It's wonderful to get someone of his calibre around the group and he'll be in a different space. His maturity and experienced over the last three years, or the previous three years in Japan. We'll add a lot of intrigue to the competition, but it is some special flavours to the Crusaders in 2027."
From a New Zealand perspective, Penney said it was great to have Mo'unga available to add depth to his position ahead of the 2027 Rugby World Cup.
"The Crusaders will be embracing him fully and trying to milk every little bit of knowledge and inspiration from him while he's here."
Mo'unga visited the Crusaders at their captain's run before, and he had given the side a message before the game.
Penney said he was like a number of the past players they drew on.
"He's still passionate about the place and him putting the boots on again and wanting to play in 2027 is an indicator of where he sees the place, but also where the place sees him."
Given the development of first five-eighths at the Crusaders, there will be no lack of resources should they retain those players when Mo'unga returns.
James White, Taha Kemara, Rivez Reihana and another emerging player in Harry Inch were players of quality, and if they are all involved, Penney said the Crusaders would be well served.
They would also gain experience by sharing time with Mo'unga, as they did with former Wallaby James O'Connor.
He said Mo'unga would be keen to play every week, but he would be managed so the needs of the Crusaders would not be compromised.
Mansbridge said Mo'unga will play out his contract in Japan, which finishes in May, but he would not be available for the latter stages of the 2026 Super Rugby Pacific competition.
"When he comes back he's available for Canterbury for the NPC and then the Crusaders for the following season."