The Yin-Yang Hot Pot Restaurant

I took over a hot pot restaurant from my second uncle. He told me never to serve customers a yin-yang hot pot after midnight! After I took over, everything I thought I knew started to fall apart... Because of a careless mistake, I served a yin-yang hot pot to a couple. The next day, I saw in the newspaper that they were dead! They had jumped off a building together in a suicide pact! Then, every night at midnight, a strange couple would appear in my restaurant, demanding that I make them a yin-yang hot pot...