The former world number one is playing her first match as a mother after giving birth to son Leo six months ago.
Azarenka had planned to come back later in the summer but brought things forward after progressing well in practice.
That decision definitely looked to be the right one when the Belarusian won the first four games against Ozaki but the Japanese player, ranked 74, turned things around.
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Ozaki was leading 3-6 6-4 5-4 and about to serve for the match when Azarenka's protests about the light were heeded and they must come back on Wednesday.
Azarenka has not played since the French Open last year, when she was already two months pregnant.
The 27-year-old currently has no ranking after being off the tour for more than a year but can enter tournaments with her protected ranking of six.
Former Wimbledon finalist Sabine Lisicki returned from her own lay-off having been out since November with a shoulder problem.
The German was tied at one-set all with fifth seed Kiki Bertens when the fifth seed retired after rolling her ankle.
Top seed Anastasia Pavlyuchenkova completed a 4-6 7-5 6-4 win over Sara Sorribes Tormo in a match held over from Monday evening.
Fourth seed Carla Suarez Navarro was upset 6-3 7-5 by fast-rising 18-year-old Cici Bellis while there were also wins for third seed Caroline Garcia and sixth seed Roberta Vinci.
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