| XTech Ventures | |
| XTIA Co., Ltd | Tokyo |
| Xtreme-D Co., Ltd | Tokyo |
| XVC, LLP | |
| Y Co., Ltd | Tokyo |
| Y!mobile | Tokyo |
| Y's Lab, Inc. | Tokyo |
| Y.A.C. Holdings Co., Ltd | Tokyo |
| Y.K. Electronics Corporation | Tokyo |
| Y4.com Co., Ltd | Tokyo |
| Yahoo Japan Corporation | Tokyo |
| Yamada Electric Ind. Co., Ltd | Tokyo |
| Yamagata Casio Co., Ltd | Tokyo |
| Yamagata Prefectural University of Health Sciences | |
| Yamagata Research Institute of Technology | |
| Yamagata University | Yamagata |
| Yamaguchi Gakugai University | |
| Yamaguchi pref. Industrial Technology Institute | |
| Yamaguchi Prefectural University | |
| Yamaguchi University | Yamaguchi |
| Yamaichi Electronics Co., Ltd | Tokyo |
| Yamanashi Eiwa College | |
| Yamanashi Gakuin University | |
| Yamanashi Internet, Inc. | Tokyo |
| Yamanashi Prefectural University | |
| Yamane Medical Co., Ltd | Tokyo |
| Yamaquchi Junior College | |
| Yamato University | |
| Yanmar Holdings Co., Ltd | |
| Yappli Co., Ltd | Tokyo |
| Yappli, Inc. | |
| Yashima Gakuen | |
| Yashimasokki Co., Ltd | Saitama |
| YASKAWA Controls Co., Ltd | |
| Yaskawa Electric Corporation | Fukuoka |
| Yaskawa Mechatrec Suematsu Kyuki Corporation | |
| Yasuda Women's University | |
| Yayoi Co., Ltd | Tokyo |
| YDC Corporation | Tokyo |
| YE DIGITAL Corporation | |
| YES Corporation | Tokyo |
| Yes We Can Co., Ltd | Tokyo |
| YL Biologics Co., Ltd | Tokyo |
| Yodogawa Hu-Tech Co., Ltd | Osaka |
| Yokkaichi Nursing and Medical Care University | |
| Yokkaichi University | |
| Yokogawa Electric Corporation | |
| Yokohama City University | |
| Yokohama College of Commerce | |
| Yokohama Densi Seiko Co., Ltd | Kanagawa |