| Atomi Gakuen | |
| ATOMica, Inc. | |
| Atomitech Co., Ltd | Tokyo |
| Atonarp Co., Ltd | Tokyo |
| Atonarp, Inc. | |
| atP's Corporation | Tokyo |
| Atrea, Inc. | |
| Atsugi Isehara Cablenetwork, Inc. | Kanagawa |
| Attack System Co., Ltd | Tokyo |
| au Payment Corporation | Tokyo |
| Audio Note Co., Ltd | Tokyo |
| Aun Consulting, Inc. | |
| Autify, Inc. | Tokyo |
| Automatigo Co., Ltd | Tokyo |
| Autoprocessing Co., Ltd | Tokyo |
| Auxilart Co., Ltd | |
| Avaldata Corporation | Tokyo |
| Avalon Technologies Co., Ltd | Tokyo |
| Avelio Systems Co., Ltd | |
| AViC Co., Ltd | Tokyo |
| AWL Co., Ltd | Tokyo |
| AWS Co., Ltd | Toyama |
| Axcelead Drug Discover Partners, Inc. | |
| Axcelead Drug Discovery Partners, Inc. | |
| Axell Corporation | Tokyo |
| Axelspace Corporation | Tokyo |
| Axis Co., Ltd | Tokyo |
| AXsolutions Co., Ltd | |
| Ayumi Trust Holdings Co., Ltd | Tokyo |
| AZ Co., Ltd | Tochigi |
| Azabu University | |
| Azbil Corporation | |
| Azbil SecurityFriday Co., Ltd | Kanagawa |
| Azden | Tokyo |
| b-mobile | Tokyo |
| B.U.G., Inc. | Tokyo |
| Baby Universe Co., Ltd | Kanagawa |
| Baidu Japan | Tokyo |
| Baika Women's University | |
| Baiko Gakuin | |
| Bancho Corporation | Tokyo |
| BANQ Corporation | Tokyo |
| Baqemono, Inc. | |
| Barrett Group Co., Ltd | Tokyo |
| BayHub Technology Co., Ltd | Tokyo |
| BBmedia, Inc. | |
| BBS Kinmei Co., Ltd | Ishikawa |
| Be-Tec Co., Ltd | Tokyo |
| Beans Computer School | Osaka |
| Beat Tech Co., Ltd | Tokyo |