The 25-year-old will join the Mitsubishi Dynaboars after the 2019 season. The Japanese club announced the deal on their Instagram page, confirming the deal was a one-year contract.
However, with the set-up of the Japanese season still unclear, Hemopo may not be available for the 2020 Super Rugby season.
In 2018, Hemopo burst onto the scene, starring for the Highlanders and earning the lock a call up to the national squad.
He went on to play three matches for the All Blacks, against France, Argentina and Japan, and joins fellow Highlanders forward Liam Squire in continuing his career in Japan following the 2019 season, with Squire signing a two-year deal with the NTT Docomo Red Hurricanes.
The Dynaboars, who won promotion into Japan's top competition last season, have also signed Sunwolves midfielder Michael Little for next season.
The former North Harbour second five-eighth has impressed in leading a revived Sunwolves squad around the park early in the 2019 Super Rugby campaign. He played a key role in the side's win over the Chiefs in Hamilton last weekend, which was the franchise's first ever away win.