G. J. Kim defeated Keisuke Saitoh 6-4 6-2 in the M15 Gimcheon 2 quarter-final on hard. The upset overturned the form book — Keisuke Saitoh came in ranked #684, leading the head-to-head 1–0. G. J. Kim claimed a first win over Keisuke Saitoh in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2025-10-28 | M15 Yanagawa City 1 | R32 | hard | Keisuke Saitoh | 4-6 6-1 6-3 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.