South Africa living in Japan but travelling to Hong Kong and Foshan in August

I am a South African Citizen teaching English in Japan. I have been to Hong kong before so I know a 30 day visa free stay is OK. However, during my stay I would like to visit Foshan, possibly overnight, and return to Hong Kong before departing for Japan again. My total trip is 12 days in Hong Kong. A local Hong Konger is a friend and guide into Foshan. My question is what do I need in order to achieve this trip into Foshan and back? Especially considering I'm living in Japan and not SA.