Ai Koga defeated Sakiko Shimizu 3-6 6-4 6-1 in the Tokyo 10K round of 16 on hard. The upset overturned the form book — Sakiko Shimizu came in leading the head-to-head 1–0. Ai Koga claimed a first win over Sakiko Shimizu in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2011-10-24 | Hamanako 25K | Q32 | carpet | Sakiko Shimizu | 6-0 6-2 |