| Computer Technology Corporation | Tokyo |
| Computermind Co., Ltd | Tokyo |
| Computex Co., Ltd | Kyoto |
| Comsoft Co., Ltd | Tokyo |
| Comture Corporation | Tokyo |
| CONNECT Co., Ltd | |
| ConnecTec Japan | Niigata |
| Connecto Data Co., Ltd | |
| Connexx Systems Corporation | Kyoto |
| Content Data Marketing Co., Ltd | Tokyo |
| Contents&Create Media Co., Ltd | Tokyo |
| ContractS Co., Ltd | Tokyo |
| Conyac | Tokyo |
| Cool Japan Fund, Inc. | |
| Cooori Japan Co., Ltd | |
| CoorsTek, Inc. | Tokyo |
| Coral Capital Co., Ltd | Tokyo |
| Coral, Inc. | Kanagawa |
| Core Corporation | Tokyo |
| Coresoft Co., Ltd | Tokyo |
| Corestaff Co., Ltd | Tokyo |
| Coretech Co., Ltd | Tokyo |
| Cornes Technologies Ltd | Tokyo |
| Cosel Co., Ltd | Toyama |
| Cosmo Intelligence Co., Ltd | Tokyo |
| Cosmo-Engineering Co., Ltd | Niigata |
| Cosmos Net Communications Co., Ltd | Tokyo |
| COSMOS, Inc. | Tokyo |
| Cosmotechs Co., Ltd | |
| Cotobank, Inc. | Tokyo |
| Cotofure Co., Ltd | Tokyo |
| Coursebase Co., Ltd | Tokyo |
| Cover Corporation | |
| CPoint Corporation | Shizuoka |
| Cradle Software Co., Ltd | Osaka |
| Crafter Co., Ltd | Tokyo |
| CREAM | |
| Creation Co., Ltd | Tokyo |
| Credit Empire Co., Ltd | Tokyo |
| Cresco Ltd | Tokyo |
| Creva Systems Co., Ltd | Tokyo |
| Creww Co., Ltd | Tokyo |
| CRI Middleware Co., Ltd | Tokyo |
| Cross Cat Co., Ltd | Tokyo |
| Cross Games Co., Ltd | Tokyo |
| Crowd Cast Ltd | Tokyo |
| CrowdWorks Co., Ltd | Tokyo |
| Cryptech Co., Ltd | Tokyo |
| CryptSoftware, Inc. | Tokyo |
| CSI Co., Ltd | Hokkaido |