While Marin and Sindhu are the favourites, Sun and Yama guchi are no pushovers.
Indian fans would be pleased to note that, were Sindhu to top Group "B", and draw Sung as her semi-final opponent, the Indian is at the right end of a 6-3 career record against the Korean, having most recently beaten Sung in the semi-finals of the 2016 China Open, after saving four match-points in a heart-stopping joust. Sindhu plays Yu next.
Akane Yamaguchi, who had lost to Sindhu on the opening day, bounced back with a stunning 18-21, 21-17, 21-14 win over Marin late Thursday to put herself in the frame for a semi-final.
Rio Olympic Games 2016 silver medallist Sindhu went down 15-21, 17-21 against World No.6 Sun at the Hamdan Sports Complex.
Axelsen, bronze medallist at the Rio Olympics, meets Lee in the final in their final group match on Friday, and the victor of that clash will go through to the semis. The Japanese then sealed the opening game after winning a long rally when Sindhu netted with a low return. Outplayed 12-21 in the opening stanza, in which she simply failed to settle down, Sindhu comprehensively turned the tables on her doughty antagonist in the second, while playing against the drift in the vast playing arena.
Sindhu kept picking a few points in between but Sun Yu reached the threshold of drawing first blood and was 20-9. Sindhu tried to neutralise her rivals deception by pushing her to the mid court and came up with a power-packed return to lead 6-3. Now, she will hope to carry that form against Sun Yu in her second match on Thursday.
"I was leading and then I gave continuous points, those points which I had to get, I made mistakes and my smashes were going into her hands. It's a crucial game and I just have to give my best and play my game".
"My lifts were going out, the points which I was going to get, was going out and also the tap, I was getting under control but then I was hitting out or into the net. I could have taken the second game but she came back and she took the lead from there", she added.
PV Sindhu is in a tough group (B) that includes world champion Carolina Marin of Spain and China's Sun Yu.
In Group A, Sung Ji-hyun and Tai Tzu-ying won their earlier matches, against He Bingjiao and Ratchanok Intanon respectively.
Downplaying the contest against Marin, Sindhu said: "I will be playing Yamaguchi first". "I've played Marc a lot of times, we know each other so well". The Indian trailed until the 15-point mark where she equalised but Sun was determined to finish the match in the second game.