Seong Yoon Chung defeated Jae Sung An 6-2 6-2 in the Japan F8 round of 16 on hard. The upset overturned the form book — Jae Sung An came in leading the head-to-head 2–0. Seong Yoon Chung claimed a first win over Jae Sung An in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2009-04-06 | Korean Rep F1 | R32 | hard | Jae Sung An | 7-5 3-6 6-4 |
| 2005-06-20 | Japan F7 | SF | clay | Jae Sung An | 6-4 7-5 |