Tomoko Yonemura defeated Seiko Okamoto 6-2 6-2 in the Hamanako 25K round of 16 on carpet. The upset overturned the form book — Seiko Okamoto came in leading the head-to-head 3–1. Tomoko Yonemura narrowed the head-to-head to 3–2.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2009-05-04 | Fukuoka 50K | R32 | grass | Tomoko Yonemura | 6-3 6-3 |
| 2007-10-15 | Makinohara 25K | R16 | carpet | Seiko Okamoto | 5-7 6-3 2-1 |
| 2005-05-23 | Nagano 25K | R16 | carpet | Seiko Okamoto | 6-4 6-7(5) 7-6(1) |
| 2002-04-15 | Gunma 10K | R16 | carpet | Seiko Okamoto | 6-2 7-5 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.