Seiko Okamoto defeated Mari Tanaka 6-2 6-3 in the Hamanako 25K round of 16 on carpet. The result followed the form book — Seiko Okamoto came in leading the head-to-head 3–0. Seiko Okamoto extended the head-to-head to 4–0.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2008-10-27 | Tokyo 50K | R32 | hard | Seiko Okamoto | 6-4 6-4 |
| 2007-04-30 | Gifu 50K | R32 | carpet | Seiko Okamoto | 6-0 4-6 7-5 |
| 2006-07-03 | Nagoya 25K | R32 | hard | Seiko Okamoto | 1-6 6-4 7-5 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.