Retimanu will guide Manase, a 27-year-old Samoan from Wellington who has mild cerebral palsy, as she attempts her first marathon.
"This is going to be a life-changing experience for Felicia," said Retimanu, who will guide Manase in the Taupo Half Marathon next weekend as she attempts her first half marathon.
"All disabled people want one thing more than anything: to be treated like everyone else. When they are running one of the most iconic races in the world, alongside some of the best runners in the world, they are achieving something remarkable and the respect of others. It is incredible to be part of that sense of achievement."
Retimanu, who had only run one marathon herself when she signed up for Achilles, knows they are in for a long day in New York. She guessed it would take them around 8-10 hours of walking and running to complete the 42.2km.
"I don't think she understands the enormity of this event," said Retimanu, who has already guided a stroke survivor from Russell through the New York Marathon in an "amazing eight-hour journey".
"The number of people doing it and the size of the challenge ahead, but that is all part of it. We are determined to get through. I cannot wait to see the look on her face as we make our way around the sights of New York."
Manase has only recently taken up running. In February she completed the Round the Bays in Wellington - it was the first time she participated in an organised running event.
"For me, finishing Round the Bays was a huge accomplishment," she said. "Because of my physical disability, I was afraid I wouldn't be able to complete it. With the support of family, partner and friends, it became a personal triumph."
Retimanu has been on her own journey of self-discovery through getting involved in the charity.
The Samoan was reading the news when it dawned on her that she didn't want to be one of the many Pacific Islanders with health problems.
"I am not athletic at all. I only started running three years ago, in a bid to change my life and get healthy as obesity rates are high among Pacific Islanders, I didn't want to become a statistic.
"I drank and smoked a lot, I ate all sorts of fast food and I never exercised. I was struggling with obesity and decided it was time to do something about it."
Retimanu began running and at the same time signed up to be involved in Achilles.
"I wondered what I had to offer but Peter [Loft] the chairman of Achilles told me that I was perfect. He said: "We don't want the best runners. We want people who are down to earth and can relate to the athletes with a disability, to people from all walks of life.
"But what people like Felicia don't realise is that she has changed my life too. Getting involved has been a massive turning point for my life."
Manase feels like a champion even before the gun goes off. She has raised the required $3000 to make the trip which is the fulfilment of a lifelong dream.
"I have always dreamed of going to the New York Marathon but never had that self-belief until reaching the finish line of Round the Bays," she said.
"This is my chance to show people that [even with] a physical disability, there is nothing I cannot achieve and also make this dream of mine come true." Manase wants to be a role model for all those who have big dreams, and show that anything is possible when you have self-belief.
"It would literally change my world. In terms of having the belief that everything is possible when you put your whole body and soul into achieving your goals. Not only mentally but physically as well."
Retimanu was on the start line of the Wellington 10km and looked across at the disabled athletes and their "amazing attitudes" and renewed her perspective.
"These guys overcome struggles every day that you or I cannot relate to. But here they are taking on massive challenges and succeeding.
"It is inspiring to be around. It shows what anyone can achieve if they want it badly enough.
"It is going to be a long day in New York but we'll get home.
"Even if I have to carry her on my back for the last few kms we will get there."
