| Challenger Nanchang Qual | 04/15 03:00 | 46 | Sekiguchi, Shuichi v Li, Yuanfeng | 6-3,6-1 | |
| Challenger - Taipei | 04/11 06:35 | 25 | [457] Sekiguchi, Shuichi v Sela, Dudi [98] | 4-6,2-6 | |
| Challenger Taipei Qual | 04/09 05:05 | 54 | [139] Bury, Aliaksandr v Sekiguchi, Shuichi [457] | Retired | |
| Challenger Taipei Qual | 04/08 07:25 | 46 | [153] Toshihide Matsui v Sekiguchi, Shuichi [456] | 5-7,6-7 | |
| Challenger Taipei Qual | 04/07 08:20 | 45 | [110] Vishnu Vardhan v Sekiguchi, Shuichi [456] | 4-6,5-7 | |
| ITF Japan F4 | 03/27 01:00 | 25 | Grills, Jacob v Sekiguchi, Shuichi | 7-6,4-6,6-3 | |
| ITF Japan F3 | 03/22 04:05 | 26 | [439] Sekiguchi, Shuichi v Katayama, Sho [425] | 5-7,6-4,2-6 | |
| ITF Japan F3 | 03/19 01:00 | 25 | Sekiguchi, Shuichi v Jumpei Yamasaki | 6-7,7-6,6-2 | |
| ITF Japan F2 | 03/12 02:30 | 25 | Hong, Seong Chan v Sekiguchi, Shuichi | 6-4,1-6,7-6 | |
| Yokohama, Japan, Qualifying | 02/24 05:10 | 45 | Hiroki Moriya v Sekiguchi, Shuichi | 6-2,6-4 | |
| Challenger Kyoto Qual | 02/17 06:10 | 45 | Kibi, Yuya v Sekiguchi, Shuichi | 6-3,6-2 | |
| Ningbo, China, Qualifying | 10/15 07:50 | 46 | Sekiguchi, Shuichi v Yunseong Chung | 4-6,3-6 | |
| Challenger Kaohsiung | 10/03 05:40 | 25 | [321] Sekiguchi, Shuichi v Akira Santillan [164] | 3-6,4-6 | |
| Challenger Kaohsiung Qual | 09/30 02:00 | 46 | Sekiguchi, Shuichi v Liu, Shao-Fan | Walkover | |
| Challenger - Gwangju | 09/19 01:30 | 25 | [322] Sekiguchi, Shuichi v Yang, Tsung-Hua [412] | 5-7,6-7 | |
| Challenger Shanghai | 09/14 02:30 | 26 | [322] Sekiguchi, Shuichi v Yibing Wu [496] | Retired | |
| Challenger Shanghai | 09/12 06:35 | 25 | [365] Kudryavtsev, Alexander v Sekiguchi, Shuichi [322] | 6-4,4-6,2-6 | |
| Zhangjiagang, China | 09/07 04:35 | 26 | [337] Sekiguchi, Shuichi v Mohamed Safwat [219] | 7-6,1-6,3-6 | |
| Zhangjiagang, China | 09/05 08:00 | 25 | [337] Sekiguchi, Shuichi v Takeuchi, Kento (1987) [414] | 6-4,6-3 | |
| Jinan, China | 08/09 03:35 | 26 | [339] Sekiguchi, Shuichi v Evgeny Donskoy [108] | 2-6,3-6 | |
| Jinan, China | 08/07 03:40 | 25 | [246] Prashanth, N. Vijay Sundar v Sekiguchi, Shuichi [350] | 4-6,4-6 | |
| Chengdu, China | 08/01 02:00 | 25 | Yunseong Chung v Sekiguchi, Shuichi | 4-6,6-3,7-5 | |
| ITF China F14 | 07/29 04:50 | 28 | [177] Nikola Milojevic v Sekiguchi, Shuichi [351] | 6-4,6-0 | |
| ITF China F14 | 07/28 03:00 | 27 | Sekiguchi, Shuichi v Singh, Karunuday | 6-3,7-6 | |
| ITF China F14 | 07/26 02:00 | 26 | Sekiguchi, Shuichi v Cao, Zhaoyi | 6-4,6-2 | |
| ITF China F14 | 07/25 05:50 | 25 | Sekiguchi, Shuichi v Kuan-Yi Lee | Retired | |
| Challenger Astana | 07/20 07:40 | 26 | [354] Sekiguchi, Shuichi v Alexander Bublik [124] | 3-6,5-7 | |
| Challenger Astana | 07/18 05:00 | 25 | [319] Zhyrmont, Dzmitry v Sekiguchi, Shuichi [354] | 2-6,6-1,3-6 | |
| Fergana, Uzbekistan | 06/21 06:30 | 26 | [204] Ilya Ivashka v Sekiguchi, Shuichi [370] | 6-2,6-2 | |
| Fergana, Uzbekistan | 06/19 06:00 | 25 | [370] Sekiguchi, Shuichi v Manafov, Vladyslav [368] | 6-4,3-6,7-5 |