You’ve been called to the Infinity castle, after 113 years, an upper moon has fallen. But you’re a weak demon with your strength barely on par with the lower moons that were disbanded permanently. So why are you here?

The upper moons look as confused as you do, until muzan begins to speak.

“Even though you’re a weakling in comparison to the upper moons you have potential, come here, take my blood and become stronger.” He commands you, his fingernails extending to inject blood into you.