Stadium: Court 4 Round: 25 Ground: Hardcourt indoor
| ITF W25 Cherbourg | 2021/10/04 08:30 | Fiona Ganz v Marthiens, Karen | 6-2,6-1 |
| ITF W25 Cherbourg | 2021/10/03 10:15 | Galvao Borges, Mariana v Marthiens, Karen | 0-6,1-6 |
| ITF W15 Dijon | 2021/09/14 11:00 | Marthiens, Karen v Anna Klasen | 1-6,1-6 |
| ITF W15 Amarante | 2021/07/20 16:00 | Marthiens, Karen v Ayla Aksu | 2-6,3-6 |
| ITF W60 Vitoria-Gasteiz | 2021/07/12 10:00 | Pulchartova, Laetitia v Marthiens, Karen | 7-5,6-4 |
| ITF W60 Vitoria-Gasteiz | 2021/07/11 09:20 | Haseth, Lilly Elida v Marthiens, Karen | 4-6,6-4,7-10 |
| ITF W25 Perigueux | 2021/06/22 08:00 | Marthiens, Karen v Guiomar Maristany Zuleta De Reales | 3-6,0-6 |
| ITF W25 Madrid | 2021/06/13 12:00 | Burguete Beltran, Andrea v Marthiens, Karen | 6-0,4-6,10-7 |
| ITF W25 Cherbourg | 2021/10/04 09:55 | Zeynep Sonmez v Himari Sato | 6-1,3-6,8-10 |
| ITF - W15 Monastir | 2021/09/29 09:40 | Anouk Koevermans v Himari Sato | 6-4,5-7,6-3 |
| ITF - W15 Monastir | 2021/09/22 13:00 | Honoka Kobayashi v Himari Sato | 7-5,6-7,6-4 |
| ITF - W15 Monastir | 2021/09/15 15:45 | Simone, Alessandra v Himari Sato | 7-5,6-3 |
| ITF W15 Almada | 2021/07/13 10:00 | Yeon Woo Ku v Himari Sato | 6-1,6-3 |
| ITF W25 Lisbon | 2021/07/05 12:35 | Himari Sato v Drummy, Georgia | 3-6,1-6 |
| ITF W25 Lisbon | 2021/07/04 14:35 | Himari Sato v Neves, Beatriz | 6-0,6-0 |
| ITF W25 Palma del Rio | 2021/06/28 16:55 | Karman Kaur Thandi v Himari Sato | 6-1,6-2 |