| AccuRna Co., Ltd | Tokyo |
| Acesoft Co., Ltd | Tokyo |
| Acompany Co., Ltd | Aichi |
| ACR Web | Osaka |
| Acrodea, Inc. | Tokyo |
| Across Co., Ltd | Tokyo |
| Acrowavenet Co., Ltd | Tokyo |
| Act Brain Co., Ltd | Tokyo |
| Act-Systems Co., Ltd | Hiroshima |
| act2, Inc. | Tokyo |
| Actnet Co., Ltd | Tokyo |
| Aculys Pharma Co., Ltd | Tokyo |
| Ad-Soft Ink | Tokyo |
| Ad-Sol Nissin Corporation | Tokyo |
| Adacotech Co., Ltd | Tokyo |
| ADAM Rental Web | Tokyo |
| Adapt Networks Co., Ltd | Tokyo |
| Adinnovation Co., Ltd | Tokyo |
| ADjust | Tokyo |
| ADM Japan | Tokyo |
| Admedia Co., Ltd | Tokyo |
| ADPRO, Inc. | Tokyo |
| ADS Co., Ltd | Chiba |
| aDsFactory | Tokyo |
| ADTEC Corporation | Tokyo |
| Advance Code, Inc. | Tokyo |
| Advanced Academic Agency | |
| Advanced Brain Corporation | Saitama |
| Advanced Core Technologies Co., Ltd | Tokyo |
| Advanced Design Corporation | Tokyo |
| Advanced Industrial Science and Technology | Tokyo |
| Advanced Institute of Industrial Technology | |
| Advanced Management Training Group Co., Ltd | Tokyo |
| Advanced Materials Technology Co., Ltd | Fukuoka |
| Advanced Photonics, Inc. | Tokyo |
| Advanced Solution Business Co., Ltd | Hyogo |
| Advanced Technologies Co., Ltd | Tokyo |
| Advanced Telecommunications Research Institute International | Kyoto |
| Advancing Quantum Architecture Research Group | Kanagawa |
| Advantest Corporation | Tokyo |
| Adways Co., Ltd | Tokyo |
| AEON Bank Ltd | Tokyo |
| Aero Development Japan Co., Ltd | Tokyo |
| Aero M's Co., Ltd | Kanagawa |
| Affiliate marketing association JAPAN | Tokyo |
| AFO Co., Ltd | Tokyo |
| Agencysoft Co., Ltd | Tokyo |
| Agile Media Network Co., Ltd | Tokyo |
| Agility Co., Ltd | Tokyo |
| AGMS Corporation | Tokyo |