Fifth seed Saina saw off Sato 21-12 14-21 21-17 in a hard-fought match that lasted 57 minutes at the Istora Gelora Bung Karno Stadium.
The world number five Indian will next take on qualifier Aprilla Yuswandaroi of Indonesia tomorrow.
Saina played long rallies and accumulated points with her better net play. After an initial fight till 6-6, Saina broke off to bag the first game and take a 1-0 lead in the match.
In the second game, Saina had a 12-5 lead but blew it off as Sato caught up with her at 13-13 before winning six straight points to level the match 1-1.
In the decider, Saina opened up a 8-1 lead and kept her nose ahead to seal the issue comfortably in the end. This was her fifth victory over Sato.
The other Olympic-bound Indian shuttlers had a mixed day with P Kashyap and mixed doubles pair of V Diju and Jwala Gutta making it to the second round. Jwala and Ashwini Ponnappa, however, lost their doubles opening round match.
In the men's singles, Kashyap survived a scare before prevailing 21-19 19-21 21-16 over Kevin Cordon of Guatemala in a match that lasted an hour and five minutes.
Diju and Jwala notched up a thrilling 14-21 21-11 21-16 victory over Korean combo of Yeon Seong Yoo and Ye Na Jang in a 50-minute match. The world number 14 Indians will next take on Tao Jiaming and Xia Huan, ranked 34th, in the second round tomorrow.