A goal just two minutes from fulltime has seen Japan snatch a 2-1 win over the Black Sticks Women at the Vantage Festival of Hockey.
In a rematch of last year's final, Japan drew first blood, when Motomi Kawamura slotted one from a penalty corner in the eighth minute.
After a first half disrupted for by a burst water main, the Japanese held their advantage deep into the fourth quarter.
The Black Sticks delivered an equalising blow in the 54th minute, thanks to a low and strong penalty corner drag-flick from Brooke Neal.
But Japan struck again with less than two minutes on the clock, when a defensive error gave away another penalty corner opportunity and allowed Yu Asai to score the winning goal.
Black Sticks midfielder Pippa Hayward said it was a game that should have ended with a draw.
"It's quite a disappointing start to the tournament for us. We need to be a lot better, and have work to do in both the attacking and defensive circles."
New Zealand will look to shake off their opening loss, when they go up against trans-Tasman rivals Australia at 5pm Saturday.
Earlier on opening day, the Hockeyroos played out a 1-1 draw with USA, with captain Alyssa Parker scoring for the United States and Madi Ratcliffe equalising for Australia early in the second half.
New Zealand 1 (Brooke Neal) Japan 2 (Motomi Kawamura, Yu Asai)