| Medical Informatics Co., Ltd | Tokyo |
| Medical Research Institute Kitano Hospital | |
| Medinet Co., Ltd | Tokyo |
| Medium Technologies Co., Ltd | Tokyo |
| MediWeb Co., Ltd | Tokyo |
| Medmain Co., Ltd | Fukuoka |
| MEDRx Co., Ltd | Kagawa |
| MEEQ Co., Ltd | Tokyo |
| Meety, Inc. | |
| Mega Technology Co., Ltd | Tokyo |
| MegaChips Corporation | Osaka |
| Megakaryon Corporation | Kyoto |
| Megasoft, Inc. | Tokyo |
| MEGATRADE Corporation | |
| Meidensha Corporation | |
| Meiho Electronics Co., Ltd | |
| Meiji Gakuin University | |
| Meiji Holdings Co., Ltd | |
| Meiji Pharmaceutical University | |
| Meiji University | |
| Meiji University of Integrative Medicine | |
| Meijo University | |
| Meikai University | |
| Meio University | |
| Meirin College | |
| Meisei Electric Co., Ltd. | |
| Meisei Gakuen Educational Corporation | Tokyo |
| Meister Corporation | Tokyo |
| Mejiro University | |
| MELEC, Inc. | |
| Memory Expert Co., Ltd | |
| Memory-Tech Corporation | Tokyo |
| Mercantile Computer Shop | Osaka |
| Mercury Software Japan, Inc. | Tokyo |
| Meritech Co., Ltd | Tokyo |
| Merx System Co., Ltd | Tokyo |
| Meson Co., Ltd | Tokyo |
| Meta Anchor, Inc. | |
| Meta Earth Co., Ltd | Tokyo |
| Metagen Co., Ltd | Yamagata |
| Metal Technology Co., Ltd | |
| Metamo Co., Ltd | Tokyo |
| MetaMoJi Corporation | Tokyo |
| Metaphase Co., Ltd | Tokyo |
| Metaplanet Co., Ltd | Tokyo |
| Metaps Holdings, Inc. | |
| Metaps Payment Co., Ltd | Tokyo |
| Metaverse Japan | Tokyo |
| Metcela Co., Ltd | Kanagawa |
| Mezurashico Ltd | |