Ayumi Oka defeated Kaori Aoyama 3-6 6-2 7-5 in the Niigata 25K round of 32 on hard. The upset overturned the form book — Kaori Aoyama came in leading the head-to-head 1–0. Ayumi Oka claimed a first win over Kaori Aoyama in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2005-10-31 | Sutama 25K | R32 | clay | Kaori Aoyama | 7-5 6-1 |