Katsuki Nagao defeated Issei Okamura 6-1 7-6 in the Japan F5 round of 32 on clay. The upset overturned the form book — Issei Okamura came in leading the head-to-head 1–0. Katsuki Nagao claimed a first win over Issei Okamura in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2015-10-05 | Philippines F1 | R16 | clay | Issei Okamura | 6-4 6-4 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.