Stadium: Court 5 Round: 25 Ground: Hardcourt outdoor
| Kofu, Qualifications Simples M-ITF-JPN-03A | 2019/03/18 06:30 | Shimizu, Keigo v Seita Watanabe | 1-6,1-6 |
| Kofu, Qualifications Simples M-ITF-JPN-03A | 2019/03/18 03:00 | Seita Watanabe v Liu, Shao-Fan | 6-3,4-6,11-9 |
| ITF - M15 Nishi-Tokyo | 2019/03/12 05:00 | Makoto Ochi v Seita Watanabe | 6-1,6-2 |
| Challenger Kobe | 2018/11/11 06:10 | Blake Ellis v Seita Watanabe | 6-4,6-2 |
| Challenger Kobe | 2018/11/10 07:20 | Seita Watanabe v Saito, Takashi | 4-6,7-5,7-6 |
| ITF Japan F8 | 2018/06/09 01:00 | Seita Watanabe v Tomohiro Masabayashi | 7-6,5-7,4-6 |
| Challenger Kobe Qual | 2017/11/04 07:45 | Seita Watanabe v Gao, Xin | 6-4,4-6,0-6 |
| ITF - M15 Nishi-Tokyo | 2019/03/12 03:20 | Tanuma, Ryota v Katayama, Sho | 6-4,2-6,10-5 |
| ITF - M15 Nishi-Tokyo | 2019/03/11 01:00 | Tange, Shota v Katayama, Sho | 3-6,3-6 |
| Nishi-Tama, Simples M-ITF-JPN-01A | 2019/03/07 04:00 | Shintaro Imai v Katayama, Sho | 6-2,6-3 |
| Nishi-Tama, Simples M-ITF-JPN-01A | 2019/03/06 02:25 | Katayama, Sho v Kawahashi, Yuta | 6-3,6-1 |
| Nishi-Tama, Simples M-ITF-JPN-01A | 2019/03/05 03:00 | Katayama, Sho v Kawahashi, Yuta | 4-6,5-7 |
| Nishi-Tama, Simples M-ITF-JPN-01A | 2019/03/05 01:00 | Katayama, Sho v Ono, Masayoshi | 6-4,6-4 |
| Canada F7, Singles | 2018/09/12 14:00 | Findel-Hawkins, Jack v Katayama, Sho | 6-3,6-3 |
| Canada F7, Singles | 2018/09/11 19:45 | Emmett Ward v Katayama, Sho | 1-6,1-6 |