- Nippon Ketjen Co., Ltd.
- N. E. Chemcat Corporation
- Sumitomo Metal Mining Siporex Co., Ltd.
- Igeta Heim Co., Ltd.
- Sumico Lubricant Co., Ltd.
- Japan Irradiation Service Co., Ltd.
- JCO Co., Ltd.
- Sumitomo Metal Mining Engineering Co., Ltd.
- Sumiko Techno-Research Co., Ltd.
- Sumiko Technical Service Co., Ltd.
- Sumiko Plantech Co., Ltd.
