There are three offices of China Southern Airlines in Shanghai:
1) No.2011, Nanjing West Road;
2) Shanghai Hongqiao Airport;
3) Shnghai Pudong Int’l Airport;
As I know, there is no flight operated by China Southern Airlines on the route of Beijing-Khabarovsk-Tokyo. However, one direct flight provided by Vladivostok Air is available on this route. From Beijing to Khabarovsk, the direct flight is available on each Monday and Thursday. While from Khabarovsk to Tokyo, one direct flight is in operation on Mondays and Fridays. Anyway, you could check with China Southern Airlines for sure.