China is building a stronger relationship with North Korea basically to boost its own flagging economy through investments. By entering into the mining sector, China will be able to extract the ores required for its own industry. Other investment to include light industry will allow China to have cheaper products for Chinese export products that are becoming expensive as the Chinese labour is no longer ready to work for crumbs as offering. By closer relationship with China, it will allow China the leverage to pressure South Korea and Japan, both of which are not taking China's activities in the SCS and elsewhere favourably. Thus, it is a win win for China.