Stadium: Court 8 Round: 25 Ground: Synthetic outdoor
| ITF Japan F7 Qual | 2018/06/03 01:00 | Onozawa, Arata v Kousuke Ogura | 6-2,6-1 |
| ITF Japan F6 | 2018/04/12 01:00 | Onozawa, Arata v Sora Fukuda | 6-7,6-4,1-6 |
| ITF Japan F6 | 2018/04/10 04:55 | Onozawa, Arata v Aoran Wang | 6-4,6-4 |
| ITF Japan F6 Qual | 2018/04/09 02:50 | Kazuki Nishiwaki v Onozawa, Arata | 7-5,6-3 |
| ITF Japan F3 | 2018/03/17 04:00 | Issei Okamura v Onozawa, Arata | 7-6,6-0 |
| Challenger Kyoto Qual | 2018/02/17 06:55 | Kim, Cheong-Eui v Onozawa, Arata | 2-6,6-3,6-4 |
| ITF Vietnam F3 | 2017/11/23 03:00 | Arjun Kadhe v Onozawa, Arata | 7-5,6-2 |
| ITF Vietnam F3 | 2017/11/21 03:00 | Onozawa, Arata v Takeshima, Shunrou | 6-0,6-3 |
| ITF Vietnam F3 | 2018/05/16 06:00 | Saito, Takashi v Song, Min-Kyu | 6-1,6-0 |
| ITF Vietnam F3 | 2018/05/14 03:00 | Saito, Takashi v Romios, Matthew Christopher | 7-6,6-1 |
| ITF Vietnam F2 | 2018/05/11 03:00 | Rio Noguchi v Saito, Takashi | 4-6,7-5,6-3 |
| ITF Vietnam F2 | 2018/05/09 03:00 | Wong, Chun Hun v Saito, Takashi | 7-6,1-6,5-7 |
| ITF Vietnam F2 | 2018/05/07 03:00 | Saito, Takashi v Moritani, Soichiro | 7-6,3-6,6-3 |
| ITF Vietnam F1 | 2018/05/04 03:00 | Vuradin, Lucas v Saito, Takashi | 7-5,6-4 |
| ITF Vietnam F1 | 2018/05/02 04:55 | Nguyen, Phuong van v Saito, Takashi | 1-6,4-6 |
| ITF Vietnam F1 | 2018/05/01 03:00 | Purcell, Rhett v Saito, Takashi | 6-7,1-6 |