He was named in the 2016 Perth-based Western Force side where he made his Super Rugby debut. Over two seasons he appeared 17 times for the team.
Since then Masirewa has been plying his trade in the Japan Top League with the Kintetsu Liners.
Masirewa is among the 36-man squad which consists of 19 players who featured in Japan's run to the World Cup quarter-finals two years ago, including captain and former Chiefs player Michael Leitch.
Former Canterbury, Hawke's Bay and Hurricanes lock Mark Abbott has also been named in the squad alongside former Otago and Highlanders prop Craig Millar.
Masirewa, Leitch, Abbott and Millar have all represented ex-Super Rugby side the Sunwolves.
Masirewa scored three tries in the Sunwolves' first ever win on Australian soil in 2019.
Japan will face the Lions in Edinburgh on June 26 before taking on Ireland in Dublin on July 3.