Natsumi Hamamura defeated Seiko Okamoto 1-6 7-6 6-1 in the Gunma 25K semi-final on carpet. The upset overturned the form book — Seiko Okamoto came in leading the head-to-head 2–0, but Natsumi Hamamura had been the form player, winning 3 of their last 6 on carpet. Natsumi Hamamura claimed a first win over Seiko Okamoto in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2006-09-18 | Ibaraki 25K | R32 | hard | Seiko Okamoto | 6-2 6-7(4) 6-1 |
| 2005-02-21 | Taipei 25K | R16 | hard | Seiko Okamoto | 6-4 7-6(6) |