Toshiaki Sakai defeated Kentaro Masuda 6-1 6-3 in the Japan F6 round of 32 on hard. The upset overturned the form book — Kentaro Masuda came in leading the head-to-head 2–0, but Toshiaki Sakai had been the form player, winning 2 of their last 4 on hard. Toshiaki Sakai claimed a first win over Kentaro Masuda in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2004-05-31 | Japan F5 | R16 | hard | Kentaro Masuda | 7-5 2-6 7-5 |
| 2004-04-12 | Japan F1 | R16 | carpet | Kentaro Masuda | 6-1 6-3 |