The opening ceremony might be on Friday but Australia's Tokyo Olympics campaign began on the softball diamond on Wednesday, where the mercy rule was invoked.
Australia lost to the hosts 8-1 after taking an early 1-0 lead.
Japan levelled the score at the end of the first innings, when catcher Tsitsikronis was called for obstruction as Naito scored the first of three runs.
The game remained locked at 1-1 until Japan's Naito smashed a two-run homer off Kaia Parnaby.
Australia, who never recovered from that blow, next face Italy in Thursday's late game.
Coach Laing Harrow described the responsibility of launching the Games as a "privilege" for his charges, who have waited for their sport to return to the Olympics since 2008.
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Women's football, alongside softball, will commence its tournament before the Tokyo Games opening ceremony - meaning the Matildas' first group match against New Zealand on Wednesday night will be prime viewing.
It's also the first time the world No.9 Matildas will be watched by a large audience in a friendly time zone under Gustavsson, after five previous friendlies.
"Just spontaneously my reaction is: what a great opportunity for us, to play with that spotlight on us and feel that," Gustavsson told AAP.
"We want to play our best when the best is needed and also that opening game is one of the most important games for us."
- with Australian Associated Press
