Ryotaro Matsumura defeated Kazuki Nishiwaki 6-4 6-2 in the M15 Karuizawa 1 round of 16 on clay. The upset overturned the form book — Kazuki Nishiwaki came in leading the head-to-head 2–0. Ryotaro Matsumura claimed a first win over Kazuki Nishiwaki in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2023-10-18 | M25 Dharwad 1 | R32 | hard | Kazuki Nishiwaki | 6-2 7-5 |
| 2023-08-01 | M15 Caloundra 2 | R32 | hard | Kazuki Nishiwaki | 6-3 3-6 6-3 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.