The background is roughly this:
Longtao has just left Tiaowei City to go to university. The day before he left, he sent his master a long confession, but got no reply. His master didn't even come out to see him off.
That same day, his master went exorcising with Xiao Jiuwuo, but an evil spirit took the opportunity to enter his body. He wasn't possessed, but had only five days left to live.
The evil spirit is so powerful that Xiao Jiuwuo can't sense it. Xiao Jiuwuo doesn't know the spirit has entered Ling Huan's body. He thinks Ling Huan is merely injured, and believes he has five years left to live.
The evil spirit's target is Maofu. The master is its medium and hostage.
Happy ending
It's cut off. There's so little food.