After English took over as Prime Minister and while Key was holidaying in Maui he took a call from Handa, who asked if he would think about being his representative and patron.
Described by Forbes magazine as "one of the most fascinating and beguiling figures in Japan", Handa's business empire includes management consultancies, publishing companies and a watch retailer.
He is an operatic baritone, Shinto priest who is a believer in reincarnation - reporting a lifeline of 20,000 years in a recent interview - expert calligraphist, avid golfer and an artist whose work has featured in a British museum exhibition.
Handa is also the founder of ISPS Handa, a not-for-profit that sponsors professional and charity events, and the Handa Foundation charity.
Handa was made an honorary member of the New Zealand Order of Merit in 2016 for services to golf and philanthropy, and has also made significant donations to the New Zealand Olympic Committee and Paralympics.
In December New Zealand football announced ISPS Handa as the new funding partner for the sport for the next three years.
Key has recently been in Australia for the Australian Golf Open and Queenstown for the New Zealand Open, both of which ISPS Handa sponsored, and in three weeks will travel to Cambodia where Handa has funded an orphanage and hospital.
"He does all sorts of stuff. He does opera in front of the [Sydney] Opera House ... and he supports the national singing scholar, just a huge range of things," Key said of Handa, who has performed with top opera stars such as Jose Carreras, Placido Domingo as well as pop star Michael Bolton.
Key spoke to the Weekend Herald from the United States and will next travel to Tokyo with wife Bronagh to attend a Handa-sponsored children's charity art exhibition and dinner.
