Ekubo is a self-proclaimed upper-class evil spirit who has aligned himself with Mob after being defeated by him.

Ekubo wants to be a god. Specifically, he wants to be worshipped by all humanity.
Despite having that kind of ego, he didn't hesitate to put himself at Mob's mercy in the hopes of using the boy to his advantage. At first, he wanted to steal Mob's body and use it to become a god, but he eventually decided to try to make Mob a god instead.