Li, the 2014 Commonwealth Games gold medallist, suffered a surprise 21-14, 21-14 defeat to the unseeded Japanese player at the Singapore Indoor Stadium.

Mitani's reward for her impressive win at the Super 500 tournament is a meeting with fifth seed and compatriot Sayaka Takahashi, who beat Shivani Gadde of India 21-8, 21-15.

Han Yue of China also recorded a shock victory as she ousted eighth seed Pornpawee Chuchawong of Thailand 21-14, 15-21, 21-19.

Han will next face Yulia Susanto after the Indonesian claimed a battling 15-21, 21-13, 21-16 triumph over India's Rituparna Das.

Nitchaon Jindapol, the highest seeded player at number two following the withdrawal of defending champion Ratchanok Intanon, safely progressed as she beat England's Chloe Birch 21-13, 21-16.

Jindapol will take on Chen Su Yu of Chinese Taipei tomorrow.

In the men's singles draw, top seed Chou Tien Chen of Chinese Taipei booked his spot in the next round as he overcame India's Subhankar Dey 21-13, 21-14.

Eighth seed Lee Hyun-il awaits for Chou in the quarter-finals after he defeated Kean Yew Loh of Singapore 21-16, 21-13.

Yu Igarashi of Japan was unable to build on his victory over defending champion Sai Praneeth Bhamidipati of India as his run at the tournament was brought to an end by China's Qiao Bin.

Bin proved far too strong for the Japanese player as he clinched a straightforward 21-14, 21-14 win.

The tournament in Singapore continues tomorrow.