Playing through Mina Tanaka in an advanced midfield role rather than playmaker Yui Hasegawa as they had against Zambia, Japan were already well in the ascendant before the double blow that knocked the stuffing out of the Central Americans.
Costa Rica, who were beaten 3-0 by Spain in their opener, were barely able to land a blow on their opponents and it looked from then on only a matter of many goals Japan would rack up.
Despite having 25 attempts on goal, however, Japan were unable to add to their tally - a shortcoming that might concern coach Futoshi Ikeda with tougher challenges lying ahead.
Japan face Spain in Wellington on Monday in a match that will almost certainly decide which of the two sides top the group, while Costa Rica will play Zambia in Hamilton at the same time as both sides continue to seek their first World Cup win.
Reporting by Nick Mulvenney in Sydney; editing by John StonestreetOur Standards: The Thomson Reuters Trust Principles.
Persons:
Aoba Fujino, Yui Hasegawa, Molly Darlington, Mina Tanaka, Hikaru Naomoto, Maria Paula Coto, Daniela Solera, Solera, Futoshi Ikeda, Nick Mulvenney, John Stonestreet
Organizations:
Soccer Football, FIFA, Costa Rica, Forsyth Barr, Costa, Dunedin, Central Americans, Zambia, Thomson
Locations:
New Zealand, Japan, Costa, Dunedin , New Zealand, Molly Darlington DUNEDIN , New Zealand, Costa Rica, Zambia, Spain, Wednesday's, Auckland, Wellington, Hamilton, Sydney