Issei Okamura defeated Kazuki Nishiwaki 6-2 6-4 in the M25 Hong Kong 1 round of 32 on hard. The upset overturned the form book — Kazuki Nishiwaki came in ranked #1176, leading the head-to-head 2–0. Issei Okamura claimed a first win over Kazuki Nishiwaki in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2018-04-09 | Japan F6 | R32 | hard | Kazuki Nishiwaki | 6-2 7-5 |
| 2017-05-22 | Singapore F1 | R32 | hard | Kazuki Nishiwaki | 7-6(3) 6-1 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.