Kei Sekine defeated Yumi Nakano 3-6 6-3 6-3 in the Niigata 10K round of 16 on carpet. The upset overturned the form book — Yumi Nakano came in leading the head-to-head 2–1. Kei Sekine narrowed the head-to-head to 2–2.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2011-03-14 | Miyazaki 10K | R32 | carpet | Yumi Nakano | 7-6(3) 6-3 |
| 2010-07-05 | Tokyo 10K | R32 | carpet | Kei Sekine | 6-7(5) 6-3 7-6(5) |
| 2008-08-25 | Saitama 10K | R32 | hard | Yumi Nakano | 7-5 7-5 |