After all, this thing called Ma Xian is an old business among the people in Northeast China. It's not complicated on the surface - some people are born with special constitutions (called "immortal destiny" in jargon), and will be selected by accomplished animal immortals to set up a hall to look after people's affairs, treat diseases, and exorcise evil spirits. The Immortal family borrows the body of younger brother Ma to accumulate merit, and the younger brother Ma relies on the Immortal family for food. The two owe nothing to each other.
But the water in this business is bottomless.
