The No.2 seed suffered a slow start to the match. Forced to defend three break points in the opening game, a wild backhand handed the 22-year-old first blood. However, the veteran American soon struck back, levelling proceedings with a cross-court volley.
Ozaki proved to be a spirited opponent in the first set and moved up a break once more to take a 3-2 lead but again failed to consolidate her advantage, sending a forehand wide to allow Williams back into the set.
Williams finally moved ahead in the final game of the first set, with Ozaki sending a volley into the net on break point after valiant defensive play.
Firmly out of the traps, the 36-year-old cruised to victory in the second set, racing into a 3-0 lead after breaking thanks to another wayward volley from Ozaki. Williams' advantage became all the more commanding after breaking once more, before wrapping up the match with a forehand winner.
"A win is a win," Williams said after the match.
"She played really well with so many defensive shots, she was very competitive and she wanted to win. It didn't matter to her that she was playing an opponent with much more experience.
"She really was motivated to win. I really respected her competitive spirit."
Williams has played well in Asia of late, winning the Dongfeng Motor Wuhan Open and WTA Elite Trophy last year, as well as reaching the semifinals in Hong Kong.
Elsewhere, Alizé Cornet beat Varvara Lepchenko, 6-3, 6-2, Louisa Chirico scored a 6-2, 6-1 win over Lee Ya-Hsuan, Daria Gavrilova defeated Zhu Lin, 6-0, 6-2, and Aleksandra Krunic cruised past Luksika Kumkhum, 6-1, 6-0.