Stadium: Court 6 Round: 62 Ground: Hardcourt outdoor
| ITF M15 Monastir | 2021/08/23 09:00 | Seita Watanabe v Samir Hamza Reguig | 6-0,6-0 |
| ITF M15 Monastir | 2021/08/22 11:00 | Seita Watanabe v Danila Moroz | 6-0,6-0 |
| ITF M15 Monastir | 2021/08/17 07:30 | Jeremy Beale v Seita Watanabe | 6-7,6-3,10-7 |
| ITF M15 Monastir | 2021/08/16 07:30 | Dylan Salton v Seita Watanabe | 0-6,2-6 |
| ITF M15 Monastir | 2021/08/12 17:05 | Mohamed Aziz Dougaz v Seita Watanabe | 6-3,0-6,6-3 |
| ITF M15 Monastir | 2021/08/11 18:10 | Seita Watanabe v Dusty H. Boyer | 6-4,6-4 |
| ITF M15 Monastir | 2021/08/10 07:30 | Rishab Agarwal v Seita Watanabe | 6-4,6-2 |
| ITF M15 Monastir | 2021/08/03 07:30 | Seita Watanabe v Martin Dimitrov | 6-7,3-6 |
| ITF M15 Monastir | 2021/08/23 09:00 | Alec Beckley v Kai Lemstra | 3-6,2-6 |
| ITF M15 Monastir | 2021/08/22 12:00 | Lucca Pinto v Kai Lemstra | 3-6,0-6 |
| ITF M15 Monastir | 2021/08/18 09:00 | Kai Lemstra v Duarte Vale | 4-6,3-6 |
| ITF M15 Monastir | 2021/08/17 07:30 | Federico Salomone v Kai Lemstra | 4-6,6-4,8-10 |
| ITF M15 Monastir | 2021/08/16 07:30 | Kai Lemstra v Blake Ellis | 6-4,6-3 |
| ITF M25 Wetzlar | 2021/08/02 14:00 | Osman Torski v Kai Lemstra | 6-4,0-6,10-5 |
| ITF M25 Most | 2021/05/26 10:15 | Antoine Escoffier v Kai Lemstra | 6-3,7-5 |
| ITF M25 Most | 2021/05/25 10:15 | Kai Lemstra v Edward Hubner | 6-1,6-1 |