Stadium: Court 7 Round: 25 Ground: Synthetic outdoor
| ITF M15 Akishima | 2019/06/11 05:00 | Shunrou Takeshima v Kosuke Okagaki | 2-6,2-6 |
| ITF M15 Akishima | 2019/06/11 00:00 | Kosuke Okagaki v Sam Ryan Ziegann | 6-1,6-0 |
| ITF M15 Antalya | 2019/04/01 07:00 | Dan Alexandru Tomescu v Kosuke Okagaki | 6-3,6-4 |
| ITF M15 Antalya | 2019/03/26 07:00 | Kosuke Okagaki v Wilson Leite | 5-7,7-5,2-6 |
| ITF M15 Antalya | 2019/03/11 07:15 | Kosuke Okagaki v Louroi Martinez | 3-6,6-2,5-10 |
| ITF M15 Antalya | 2019/02/25 14:45 | Mircea-Alexandru Jecan v Kosuke Okagaki | 6-4,6-0 |
| ITF M15 Antalya | 2019/02/25 07:00 | Kosuke Okagaki v Moritz Thiem | 3-6,7-6,10-3 |
| ITF Japan F1 | 2018/03/03 01:00 | Kosuke Okagaki v Naoto Kai | 6-4,0-6,2-6 |
| ITF M15 Akishima | 2019/06/11 04:45 | Tamaki Yamao v Len Schouten | 6-3,7-6 |
| ITF M15 Akishima | 2019/06/11 00:00 | Tamaki Yamao v Taisei Miyamoto | 6-4,2-6,10-4 |
| ITF M15 Kashiwa | 2019/04/04 05:30 | Sho Shimabukuro v Tamaki Yamao | 6-2,2-6,6-2 |
| ITF M15 Kashiwa | 2019/04/03 03:05 | Tamaki Yamao v Naoki Tajima | 6-1,3-6,6-2 |
| ITF M15 Kashiwa | 2019/04/01 00:00 | Ryota Tanuma v Tamaki Yamao | 6-7,4-6 |
| ITF M15 Kashiwa | 2019/04/01 00:00 | Tamaki Yamao v Mick Veldheer | 6-1,6-4 |
| ITF M15 Tsukuba | 2019/03/25 04:30 | Mick Veldheer v Tamaki Yamao | 6-1,6-3 |
| ITF M15 Tsukuba | 2019/03/25 01:00 | Tamaki Yamao v Hao Yuan Ng | 6-3,6-2 |