Ground: Clay
| ITF Japan F7 Qual | 2015/06/15 00:30 | Renta Tokuda v Numajiri, Keisuke | 3-6,1-6 |
| ITF Japan F7 Qual | 2015/06/13 00:00 | Kai, Naoto v Numajiri, Keisuke | 2-6,3-6 |
| ITF Japan F6 Qual | 2015/06/07 05:00 | Sano, Koichi v Numajiri, Keisuke | 6-0,4-6,6-1 |
| ITF USA F16 | 2015/05/09 16:00 | Lunn, Justin v Numajiri, Keisuke | 3-6,2-6 |
| ITF USA F16 | 2015/05/08 20:00 | Donaldson, Brandon v Numajiri, Keisuke | 1-6,2-6 |
| ITF USA F14 | 2015/04/29 15:30 | Numajiri, Keisuke v Facundo Mena | 6-7,3-6 |
| ITF USA F14 | 2015/04/27 15:00 | Li, Yuanfeng v Numajiri, Keisuke | 3-6,2-6 |
| ITF Japan F4 | 2015/03/29 00:00 | Numajiri, Keisuke v Onoda, Ken | 6-0,1-6,6-3 |
| ITF Japan F8 | 2015/06/24 02:45 | Watanuki, Keisuke v Ito, Yuichi | 6-1,7-5 |
| ITF Japan F7 | 2015/06/16 02:15 | Onozawa, Arata v Watanuki, Keisuke | 7-6,0-6,6-3 |
| ITF Japan F6 | 2015/06/11 02:55 | Niki, Takuto v Watanuki, Keisuke | 6-7,7-6,6-4 |
| ITF Japan F6 | 2015/06/10 01:30 | Watanuki, Keisuke v Oku, Hiromasa | 6-2,6-3 |
| ITF Japan F5 | 2015/06/04 02:00 | Thomas Fancutt v Watanuki, Keisuke | 7-5,7-6 |
| ITF Japan F5 | 2015/06/03 06:30 | Ryotaro Matsumura v Watanuki, Keisuke | 6-2,4-6,0-6 |
| ITF Greece F9 | 2015/04/29 10:05 | Simunek, David v Watanuki, Keisuke | 6-4,6-2 |
| ITF Greece F5 | 2015/04/23 07:00 | Kocevar-Desman, Tom v Watanuki, Keisuke | 6-3,6-2 |