Bull Demon King and the others were demons in the Human World, while the immortals of the Heavenly Court were naturally their enemies. Son Goku going to serve as an official in the Heavenly Court was tantamount to betraying Bull Demon King and the others.
With Son Goku's Early-Stage Golden Immortal cultivation, once he entered the Heavenly Court, he could at least secure a position as a Heavenly General.
But why did the Jade Emperor appoint Son Goku as nothing more than a mere Keeper of Horses? Was it not simply to humiliate Bull Demon King and the others?
After all, Son Goku and Bull Demon King's group were collectively known as the Seven Great Sages, and for a time, their fame had been unparalleled. Yet Son Goku had now become a Keeper of Horses.
Wasn't that practically saying that once Bull Demon King and the other Seven Great Sages went to Heaven, they could only become horse keepers for the Jade Emperor? It was simply a complete loss of face for the Seven Great Sages.
Unfortunately, Son Goku knew nothing of the schemes involved. After Venus sweet-talked him for a while, he happily ran off to the Heavenly Court to become its Keeper of Horses.
If Son Goku himself did not understand the trap, Bull Demon King and the others should have understood, shouldn't they?
But Son Goku was wholly focused on becoming an official in the Heavenly Court. How could he still remember his six sworn brothers?
If Son Goku had truly valued loyalty, he would certainly have informed Bull Demon King and the others before going to the Heavenly Court.
If he had done so, Bull Demon King and the others would definitely not have let Son Goku go to the Heavenly Court, and none of what