| SIIX Corporation | Tokyo |
| Silex Technology | Tokyo |
| Silicon Arts Design & Concert Fidelity, Inc. | Nagano |
| Silicon Studio Corporation | Tokyo |
| Simpleasy, Inc. | |
| Simplex, Inc. | Tokyo |
| Sinfonia Technology Co., Ltd | Tokyo |
| SIOS Technology Co., Ltd | Tokyo |
| SIP Global Partners | |
| SIS Techno Service Co., Ltd | Tokyo |
| Sisco Consulting Co., Ltd | Tokyo |
| sk-design | Tokyo |
| Sky Brains Co., Ltd | Kanagawa |
| SKY Perfect JSAT Corporation | Tokyo |
| SKY Perfect JSAT Holdings Co., Ltd | Tokyo |
| Skydisc Co., Ltd | Fukuoka |
| SkyDrive Co., Ltd | Aichi |
| Skygate Technologies, Inc. | |
| Skyland Ventures | Tokyo |
| Skynet Co., Ltd | Tokyo |
| Slogical Corporation | Tokyo |
| Smart Capital Co., Ltd | Tokyo |
| Smart Codes Co., Ltd | Tokyo |
| Smart Idea Co., Ltd | Tokyo |
| Smart Robotics Co., Ltd | Tokyo |
| Smart Share Co., Ltd | Tokyo |
| Smart Shopping Co., Ltd | Tokyo |
| Smart Style Co., Ltd | Tokyo |
| Smart Trade Co., Ltd | Tokyo |
| Smartcamp Co., Ltd | Tokyo |
| SmartDrive Co., Ltd | Tokyo |
| SmartHR Co., Ltd | Tokyo |
| SmartHR, Inc. | |
| SmartRyde, Inc. | |
| SMBC Venture Capital Co., Ltd | Tokyo |
| SMC Corporation | |
| sMedio Co., Ltd | Tokyo |
| SMK Corporation | Tokyo |
| SMN Corporation | Tokyo |
| SMSDataTech Corporation | Tokyo |
| SNI | Saga |
| SNIA Japan | Tokyo |
| Snit Computer Co., Ltd | Hokkaido |
| SO Technologies Co., Ltd | Tokyo |
| Soai University | |
| SocialDog, Inc. | |
| Sociomedia, Inc. | Tokyo |
| SOCIUM Co., Ltd | Tokyo |
| SODA Co., Ltd | Tokyo |
| Sofix Co., Ltd | |