| Challenger Nanchang Qual | 04/15 03:00 | 46 | Shuichi Sekiguchi v Yuanfeng Li | 6-3,6-1 | |
| Challenger Taipei | 04/11 06:35 | 25 | [457] Shuichi Sekiguchi v Dudi Sela [98] | 4-6,2-6 | |
| Challenger Taipei Qual | 04/09 05:05 | 54 | [139] Aliaksandr Bury v Shuichi Sekiguchi [457] | Retired | |
| Challenger Taipei Qual | 04/08 07:25 | 46 | [153] Toshihide Matsui v Shuichi Sekiguchi [456] | 5-7,6-7 | |
| Challenger Taipei Qual | 04/07 08:20 | 45 | [110] Vishnu Vardhan v Shuichi Sekiguchi [456] | 4-6,5-7 | |
| ITF Japan F4 | 03/27 01:00 | 25 | Jacob Grills v Shuichi Sekiguchi | 7-6,4-6,6-3 | |
| ITF Japan F3 | 03/22 04:05 | 26 | [439] Shuichi Sekiguchi v Sho Katayama [425] | 5-7,6-4,2-6 | |
| ITF Japan F3 | 03/19 01:00 | 25 | Shuichi Sekiguchi v Jumpei Yamasaki | 6-7,7-6,6-2 | |
| ITF Japan F2 | 03/12 02:30 | 25 | Seong Chan Hong v Shuichi Sekiguchi | 6-4,1-6,7-6 | |
| Challenger Yokohama Qual | 02/24 05:10 | 45 | Hiroki Moriya v Shuichi Sekiguchi | 6-2,6-4 | |
| Challenger Kyoto Qual | 02/17 06:10 | 45 | Yuya Kibi v Shuichi Sekiguchi | 6-3,6-2 | |
| Challenger Ningbo Qual | 10/15 07:50 | 46 | Shuichi Sekiguchi v Yunseong Chung | 4-6,3-6 | |
| Challenger Kaohsiung | 10/03 05:40 | 25 | [321] Shuichi Sekiguchi v Akira Santillan [164] | 3-6,4-6 | |
| Challenger Kaohsiung Qual | 09/30 02:00 | 46 | Shuichi Sekiguchi v Shao-Fan Liu | Walkover | |
| Challenger Gwangju | 09/19 01:30 | 25 | [322] Shuichi Sekiguchi v Tsung-Hua Yang [412] | 5-7,6-7 | |
| Challenger Shanghai | 09/14 02:30 | 26 | [322] Shuichi Sekiguchi v Yibing Wu [496] | Retired | |
| Challenger Shanghai | 09/12 06:35 | 25 | [365] Alexander Kudryavtsev v Shuichi Sekiguchi [322] | 6-4,4-6,2-6 | |
| Challenger Zhangjiagang | 09/07 04:35 | 26 | [337] Shuichi Sekiguchi v Mohamed Safwat [219] | 7-6,1-6,3-6 | |
| Challenger Zhangjiagang | 09/05 08:00 | 25 | [337] Shuichi Sekiguchi v Kento Takeuchi [414] | 6-4,6-3 | |
| Challenger Jinan | 08/09 03:35 | 26 | [339] Shuichi Sekiguchi v Evgeny Donskoy [108] | 2-6,3-6 | |
| Challenger Jinan | 08/07 03:40 | 25 | [246] N. Vijay Sundar Prashanth v Shuichi Sekiguchi [350] | 4-6,4-6 | |
| Challenger Chengdu | 08/01 02:00 | 25 | Yunseong Chung v Shuichi Sekiguchi | 4-6,6-3,7-5 | |
| ITF China F14 | 07/29 04:50 | 28 | [177] Nikola Milojevic v Shuichi Sekiguchi [351] | 6-4,6-0 | |
| ITF China F14 | 07/28 03:00 | 27 | Shuichi Sekiguchi v Karunuday Singh | 6-3,7-6 | |
| ITF China F14 | 07/26 02:00 | 26 | Shuichi Sekiguchi v Zhaoyi Cao | 6-4,6-2 | |
| ITF China F14 | 07/25 05:50 | 25 | Shuichi Sekiguchi v Kuan-Yi Lee | Retired | |
| Challenger Astana | 07/20 07:40 | 26 | [354] Shuichi Sekiguchi v Alexander Bublik [124] | 3-6,5-7 | |
| Challenger Astana | 07/18 05:00 | 25 | [319] Dzmitry Zhyrmont v Shuichi Sekiguchi [354] | 2-6,6-1,3-6 | |
| Challenger Fergana | 06/21 06:30 | 26 | [204] Ilya Ivashka v Shuichi Sekiguchi [370] | 6-2,6-2 | |
| Challenger Fergana | 06/19 06:00 | 25 | [370] Shuichi Sekiguchi v Vladyslav Manafov [368] | 6-4,3-6,7-5 |