Kaori Aoyama defeated Ayumi Oka 7-5 6-1 in the Sutama 25K round of 32 on clay. The upset overturned the form book — Ayumi Oka came in leading the head-to-head 1–0. Kaori Aoyama claimed a first win over Ayumi Oka in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2011-05-23 | Niigata 25K | R32 | hard | Ayumi Oka | 3-6 6-2 7-5 |