The Land of the Rising Sun drew first blood in the ninth minute - the second of penalty-corner attempts after Marina Yagi had missed the first attempt - from striker Motomi Kawamura raising her stick in triumph after emerging from a scrum as the Kiwi new signing goalkeeper, Grace O'Hanlon, couldn't prevent the prod from a scrambling defence despite lying across the face of the goalmouth.
The visitors, rebuilding after Rio Olympics like all teams, fell back on defence soon after to thwart a wave of Kiwi attacks amid some spirit-lifting cheering from their dugout.
They then became the architects of a well thought out counterattack, typical of Asian countries, to yield another penalty corner but couldn't convert.
Japan defender Emi Nishikori was simply outstanding, thwarting any preconceived ideas the hosts may have had about weaving phases of attack.
Like the Hockeyroos earlier, coach Mark Hager's women seemed content to go through the motions as the Japanese showed more assertiveness in the engine room.
The disastrous flooding was a blessing in disguise for Hager who got his troops back on the same page during the enforced extended break as the Kiwis came out with more mongrel.
The game came to a flooding halt about 6.37pm at the Hastings City end of the international Unison Stadium turf at the Hawke's Bay Regional Sports Park.
Oblivious to the commotion, the players carried on with the game, until a Black Sticks player and Japanese counterpart chased a runway pass to the offending corner to realise the ball had rolled into ankle deep water encroaching the arena like a rising tide at Marine Parade along Napier City.
They turned around, looking perplexed, before the stadium announcer brought the flooding to the attention of the match officials on the park.
An army of stadium staff and volunteers waded through the water that had snaked its to the rear entrance of the stadium forming a murky moat.
The workers strategically planted wooden crate-like makeshift bridges to enable fans to walk over it to dry land on the other side of the enclosure.
The fire department arrived as officers employed super hoses to soak up water before squirting it on to the adjacent lawn in front of the Hawke's Bay Netball courts.
The game resumed at 7.30pm after a sterling clean-up exercise.