Osaka will bid for her second Grand Slam title in succession against twice Wimbledon champion Kvitova on Saturday, having claimed her maiden major in New York last year by upsetting Serena Williams in the final.
Serena Williams battled a misbehaving serve and scorching heat but stayed cool under pressure in a 7-5, 6-4 win over Czech Barbora Strycova to reach the Australian Open quarter-finals on Monday.
Halep has struggled for form and fitness since her first-round defeat at the US Open last August and came to Australia on a five-match losing streak and without a coach after long-serving Darren Cahill left for "family reasons".
Images from the Australian Open in Melbourne on Thursday.
IMAGES from the Australian Open matches played at Melbourne Park on Wednesday