Whiley, returning to Australia for the first time since 2016 after making a comeback from maternity leave, lost 6-2 7-6 (7-5) to the Japanese second seed.

The pair will team up in the doubles, having won the titles in Melbourne in 2014 and 2015.

Elsewhere, Britain's Andy Lapthorne won his opening men's quad singles match.

The second seed beat his American doubles partner David Wagner 6-3 7-6 (8-6) and will take on Australian Dylan Alcott in his next match as part of a round-robin format.

Other Britons in action on Wednesday include US Open champion Alfie Hewett, who faces French fourth seed Stephane Houdet in the men's singles, while 2016 Australian Open winner Gordon Reid is up against Argentine world number two Gustavo Fernandez.