Asked if Toulouse were happy with his decision, Johnston said: "Not at the moment. I'm still in talks with them at the moment - I'm explaining to them that my country needs help and it's something that I want to do.
"In Samoan culture if someone asks for help you can't let them down; especially on an occasion like this. Personally this is something I haven't done. I've played 50 tests and none against the All Blacks. It was something to tick-off for me."
It's no secret that European clubs would prefer their players not to represent their countries - especially those from afar in the Pacific Islands. Clubs have offered the Islands players improved contracts on the basis that they retire from the international game, and that is the decision Johnston originally made, prompted also by some robust statements he has made about the state of the Samoan Rugby Union.
"Contract-wise the club offered something I couldn't refuse. It was tough because in November we didn't know how the union were going to react, especially with me and Daniel Leo coming out with a lot of stuff.
"I didn't want to say no to something and then get let down by the union [but] I'm here and I'm just happy to be part of it."
Johnston recently signed another three-year deal with Toulouse, whom he represented in a semifinal against Clermont three weeks ago, but a part of him would like to return his family - his wife and three children aged under 7 - to New Zealand.
"I've talked to my wife in the last couple of days and we're nearly getting to the point where we're ready to come home. France has been good to us - we've been in Europe for the last 10 years. Sometimes you just know when it's time.
"My kids are getting older now and they're pretty much French. They have been raised in the French language and we're a bit worried that we're going to come back and they're going to be a bit behind schooling-wise."
So, in front of his mum, who lives in Auckland but has stayed in Samoa after the wedding, Johnston is preparing to play what will probably be one of his last tests.
The strongman of the team isn't fazed if the All Blacks try to push his pack around, either. He'll be the big one in blue up front holding things together.
"Half of the group are playing in Europe so we're used to scrummaging and mauling, pretty much 60-70 per cent of the game. It's something we're prepared to do. The only worry for us is if the ABs try to run us around for 80 minutes."