Nikkei press reported 2015 stainless steel market share in Japan. According to it, the top supplier was Nippon Steel & Sumitomo Metal (32%).
Figure: 2015 Stainless Steel Market Share in Japan
|Manufacturer||Market share (%)|
|Nippon Steel & Sumitomo Metal||32.0|
|Nippon Yakin Kogyo||9.0|
Source is Nikkei Sangyo Shimbun newspaper, the article on 2016 July 25th.