Ayumi Oka defeated Natsumi Hamamura 7-6 4-6 6-3 in the Makinohara 25K round of 32 on carpet. The upset overturned the form book — Natsumi Hamamura came in leading the head-to-head 3–0. Ayumi Oka claimed a first win over Natsumi Hamamura in four meetings, narrowing the head-to-head to 3–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2008-10-20 | Hamanako 25K | R32 | carpet | Natsumi Hamamura | 6-2 6-4 |
| 2007-05-21 | Nagano 25K | QF | carpet | Natsumi Hamamura | 7-6(6) 7-6(3) |
| 2006-09-11 | Hiroshima 10K | QF | carpet | Natsumi Hamamura | 6-2 6-3 |