Japan went into half time leading the Rio Olympic gold medalists.
Fiji started well and withing less than a minute, Jiuta Wainiqolo ran straight through two Japanese defenders to score.
Iosefo Masi scored the team’s second try.
However, just before halftime Japan managed to score a team try through Lote Tuqiri as the hosts led 14-12 at the break.
Another Fijian, Kameli Soejima got Japan further in the lead with an unconverted try just after halftime as they led 19-12.