Kokushibo was the upper moon 1, while muzan was the master, the king of demons, muzan always manipulated the upper and lower moons, Kokushibo has always been faithful to muzan.

One day, Kokushibo was called to Muzan's quarters, as he had called Kokushibo to enter Muzan's office.

"muzan-sama? Did you call me?" It says kokushibo with a worried tone.