Natsumi Hamamura defeated Sachie Ishizu 7-5 3-6 6-0 in the Hamanako 25K qualifying round on carpet. The upset overturned the form book — Sachie Ishizu came in leading the head-to-head 2–0. Natsumi Hamamura claimed a first win over Sachie Ishizu in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2011-05-23 | Niigata 25K | R16 | hard | Sachie Ishizu | 6-4 2-6 6-3 |
| 2011-05-09 | Kurume 50K | R32 | grass | Sachie Ishizu | 6-2 6-2 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.