| RION Co., Ltd | Tokyo |
| Riso Kagaku Corporation | Tokyo |
| Rissho University | Tokyo |
| RisuMail | Tokyo |
| Ritsumeikan Asia Pacific University | |
| Ritsumeikan University | |
| Ritsumeikan University - Department of Computer Science | Kyoto |
| RIV Co., Ltd | Okinawa |
| RKC Instrument Co., Ltd | Tokyo |
| Robit Co., Ltd | Tokyo |
| Robot Communications Co., Ltd | Tokyo |
| Robot Payment Co., Ltd | Tokyo |
| Robot Start Co., Ltd | Tokyo |
| Robotics Society of Japan | Tokyo |
| Rock Garage Co., Ltd | Ibaraki |
| Rocket3.net | Tokyo |
| Rohm Co., Ltd | Tokyo |
| ROHTO Pharmaceutical Co., Ltd | |
| Roland DG Corporation | Shizuoka |
| Rooter Co., Ltd | Tokyo |
| RootPro Co., Ltd | Nagano |
| Rorze Corporation | Hiroshima |
| RPA Solutions Co., Ltd | Tokyo |
| RPlanning Co., Ltd | Gunma |
| RS Technologies Co., Ltd | Tokyo |
| RT Co., Ltd | Tokyo |
| Rubycon Corporation | Nagano |
| Ryokosha Corporation | Tokyo |
| Ryomo Internet | Tokyo |
| Ryomo Systems Co., Ltd | Tokyo |
| Ryosan Co., Ltd | |
| Ryu-Raku, Inc. | |
| Ryukoku University | |
| Ryukoku University - Department of Applied Mathematics and Informatics | Shiga |
| Ryutsu Keizai University | |
| S.E.R. Corporation | Tokyo |
| SAEILO, Inc. | Saitama |
| SAEILO-Telecom | Chiba |
| Saga University | Saga |
| Saga University - Department of Mathematics | Saga |
| Sagami Chemical Research Institute | |
| Sagami Women's University | |
| Sagant Antenna | Saga |
| Sagri Co., Ltd | Tokyo |
| SAIHI information service Ltd | Saga |
| SaiNet Corporation | Saitama |
| Saishunkan System Co., Ltd | Tokyo |
| Saitama Fuji Co., Ltd | |
| Saitama Gakuen University | |
| Saitama Institute of Technology | |