| 1. Round | 28/02/2021 | Mito HollyHock | - | RB Omiya Ardija | 1:2 | ||||
| 2. Round | 06/03/2021 | RB Omiya Ardija | - | Ventforet Kofu | 0:2 | ||||
| 4. Round | 21/03/2021 | SC Sagamihara | - | RB Omiya Ardija | 2:1 | ||||
| 5. Round | 27/03/2021 | RB Omiya Ardija | - | V-Varen Nagasaki | 4:0 | ||||
| 6. Round | 03/04/2021 | FC Ryūkyū | - | RB Omiya Ardija | 0:0 | ||||
| 7. Round | 10/04/2021 | Blaublitz Akita | - | RB Omiya Ardija | 0:0 | ||||
| 13. Round | 09/05/2021 | Thespakusatsu Gunma | - | RB Omiya Ardija | 1:1 | ||||
| 20. Round | 27/06/2021 | Renofa Yamaguchi | - | RB Omiya Ardija | 0:1 | ||||
| 21. Round | 03/07/2021 | RB Omiya Ardija | - | Montedio Yamagata | 1:3 | ||||
| 25. Round | 14/08/2021 | RB Omiya Ardija | - | Blaublitz Akita | 1:1 | ||||
| 32. Round | 03/10/2021 | Tochigi SC | - | RB Omiya Ardija | 1:3 | ||||
| 37. Round | 03/11/2021 | Kyoto Sanga FC | - | RB Omiya Ardija | 1:0 | ||||
| 38. Round | 07/11/2021 | RB Omiya Ardija | - | Renofa Yamaguchi | 1:2 | ||||
| 41. Round | 28/11/2021 | FC Machida Zelvia | - | RB Omiya Ardija | 0:0 |  |
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| 42. Round | 05/12/2021 | RB Omiya Ardija | - | Thespakusatsu Gunma | 3:1 |
Japan