Hinata Miyazawa scored twice as former champions Japan smashed Women's World Cup newcomers Zambia 5-0 in a rampant start to their campaign on Saturday.
Japan were a class above the 77th-ranked Africans, creating a slew of chances with their sharp movement and passing in a performance that will have the tournament heavyweights on alert.
Three of the goals came through sweeping upfield movements as Japan scored more than twice in a World Cup game for the first time since the 2011 tournament in Germany, when they lifted the title.
Midfielder Miyazawa bagged her first midway through the first half from an Aoba Fujino assist to put the Nadeshiko a goal up at the break.
Mina Tanaka doubled the lead from Jun Endo's cross, bringing some relief to the forward, who found the net twice earlier in the match, only to have both strikes ruled out by belated offside rulings.
Tanaka turned provider for Miyazawa's second goal and Endo drilled home the fourth in front of a crowd of 16,111 in Hamilton.
Substitute Riko Ueki scored the final goal from the penalty spot after she was brought down by goalkeeper Catherine Musonda in the final minute of stoppage time.
It resulted in a second yellow card for Musonda, whose replacement Eunice Sakala made a spectacular save from the spot but was ruled to have moved too early.
Ueki made no mistake with her second attempt as Japan moved to the top of Group C ahead of Spain, who beat Costa Rica 3-0 in Wellington on Friday.
A youthful Zambian side entered the tournament with high hopes after beating Germany in their final warmup game.
However, the lowest-ranked side at the 32-team tournament didn't create a single clear chance, capping a miserable week in which key attacking midfielder Grace Chanda was ruled out of the tournament with illness.
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