- GRANOPT Ltd.
- Igeta Heim Co., Ltd. (Japanese Version Only)
- Japan Irradiation Service Co., Ltd. (Japanese Version Only)
- Mitsui Sumitomo Metal Mining Brass & Copper Co., Ltd. (Japanese Version Only)
- N. E. Chemcat Corporation
- Nippon Ketjen Co., Ltd.
- Nittosha Co., Ltd. (Japanese Version Only)
- Shinko Co., Ltd. (Japanese Version Only)
- Sumico Lubricant Co., Ltd.
- Sumiko Eco-engineering Co., Ltd.
- Sumiko Logistics Co., Ltd. (Japanese Version Only)
- Sumiko Plantech Co., Ltd. (Japanese Version Only)
- Sumiko Resources Exploration & Development Co., Ltd.
- Sumiko Techno-Resarch Co., Ltd. (Japanese Version Only)
- SumikoTec Co., Ltd. (Japanese Version Only)
- Sumitomo Metal Mining Siporex Co., Ltd. (Japanese Version Only)
- Taihei Metal Industry Co., Ltd.
- Jinglong Copper Co., Ltd.
- Malaysian Electronics Materials SDN. BHD
- Sumitmo Metal Mining Asia Pacific Pte.Ltd.
- SMM Solomon Ltd.
