Fourth seed Saina took 33 minutes to beat Mingtian 21-17 21-16. She will take on Juan GU of Singapore tomorrow.
Commonwealth Games bronze medallist P Kashyap played his heart out before going down 15-21 21-6 18-21 to sixth seed Jin Chen in the men's singles match which lasted for one hour and six minutes.
Ajay Jayaram, who stunned World number seven Tien Minh Nguyen yesterday, also became a second round casualty after losing 20-22 16-21 to Indonesian Simon Santoso in a 42-minute battle.
Commonwealth Games gold medallist Jwala Gutta and Ashwini Ponnappa also failed to get past seventh seeded Jung Eun Ha and Min Jung Kim in the women's doubles event.
The Indian duo lost 9-21 21-18 22-24 to the Korean pair in 49 minutes.
The Indian mixed doubles pair of Jwala and V Diju also lost their second round battle 15-21 10-21 against fifth seeded pair of Hung Ling Chen and Wen Hsing Cheng in just 24 minutes.
The 21-year-old Saina, however, kept India's tricolour fluttering at the Tokyo Metropolitan Gymnasium.
In the first game, Saina opened up a narrow 9-5 lead and though Mingtian caught up with her at 14-all, the Indian was able to held her fort to get ahead.
In the second game, Mingtian dominated the initial proceedings and had her nose ahead at 6-4 but Saina drew parity at 13-all and then broke off at 15-15 with six straight points to seal her place in the quarterfinals.
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