Issei Okamura defeated Ryota Tanuma 6-3 7-6 in the China F13 semi-final on clay. The upset overturned the form book — Ryota Tanuma came in ranked #1316, leading the head-to-head 5–2. Issei Okamura narrowed the head-to-head to 5–3.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2025-03-24 | M15 Tsukuba 1 | Q16 | hard | Issei Okamura | 6-0 7-5 |
| 2020-02-26 | M15 Sharm El Sheikh 4 | R32 | hard | Ryota Tanuma | 6-3 6-2 |
| 2019-03-22 | M15 Kofu 1 | QF | hard | Ryota Tanuma | 6-4 6-2 |
| 2018-01-08 | China F1 | R16 | clay | Ryota Tanuma | 6-1 6-2 |
| 2016-05-16 | Spain F14 | R32 | clay | Ryota Tanuma | 6-0 6-3 |
| 2015-08-17 | Chinese Taipei F1 | QF | hard | Issei Okamura | 6-4 3-6 6-3 |
| 2015-06-01 | Japan F5 | R32 | clay | Ryota Tanuma | 7-6(0) 6-4 |
Averages over each player's completed matches in the selected window (200 vs 200). ATP, WTA & Challenger.
Each player's serve crossed against the other's return, converted to expected hold of serve. Recent completed matches, ATP, WTA & Challenger. About