What is the relationship between Meng Po and Yan?

The two roles are superior and subordinate in the underworld.

1, Yan is the manager of the underworld, equivalent to the emperor of the human world, enough to command all creatures in the underworld, and is the supreme existence of the underworld.

2. Meng Po, a man from the underworld, is responsible for making soup for the dead, so that everyone can drink Meng Po's soup that can forget all the memories of past lives, thus stepping into reincarnation.