Ryotaro Matsumura defeated Naoki Tajima 3-6 6-1 6-4 in the M15 Karuizawa 1 round of 32 on clay. The upset overturned the form book — Naoki Tajima came in leading the head-to-head 2–0. Ryotaro Matsumura claimed a first win over Naoki Tajima in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2023-04-02 | M25 Kashiwa 1 | Q32 | hard | Naoki Tajima | 6-4 4-0 |
| 2023-03-27 | M25 Tsukuba 1 | Q16 | hard | Naoki Tajima | 6-3 0-6 10-4 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.