The Asian outfit dominated possession early on, with Aoba Fujino their main attacking presence. The forward had two terrific chances to open the scoring within the opening 10 minutes, first seeing one shot tipped over the bar, before rattling the woodwork with a terrific drive from distance.
Mina Tanaka then had a goal ruled out for offside while Zambia goalkeeper Catherine Musonda made another fine stop from Fuka Nagano’s deflected strike.
The Copper Queens, who are participating in the World Cup for the first time, were living life dangerously as they struggled to break out of their own half, and their resolve was eventually broken on the stroke of half time as Miyazawa converted Fujino’s cross from inside the area.
That threatened to open the floodgates, but Zambia were riding their luck, as firstly a strike from Tanaka and then a penalty awarded for a foul by Musonda on Fujuno were both chalked off for narrow offsides.
Tanaka would eventually make it third time lucky though, sliding in to convert from Jun Endo’s cross and doubling the Japanese lead.
By now, Bruce Mwape’s side were all over the place, and Japan made it 3-0 shortly after the hour mark when Miyazawa tapped home her second from close range.
Endo then clinically slid into the bottom corner after bursting into the box to stretch their advantage to four, while only a magnificent goalline clearance from Martha Tembo stopped Riko Ueki from adding a fifth.
That goal eventually came deep into added time when Musonda brought down Ueki in the area, conceding a penalty and being sent off in the process. Ueki converted the resulting spot-kick at the second time of asking.
That rounded off a chastening evening for Zambia, who would have dreamed of springing a shock on their World Cup debut, but in the end failed to register a single shot as they slumped to a heavy defeat.
Japan could now book their place in the knockout stages by beating Costa Rica on Wednesday.
Flashscore Player of the Match: Aoba Fujino (Japan)
