Son of Muzan

What would happen if Muzan had a son before becoming the demon he was? Well Roku was born from Muzan and a women Muzan slept woh before he became a demon. Once he is born Muzan adopts him and chooses to turn him into a demon once he reaches he age of 18. Roku is the strongest demon aside from Muzan but he hopes to become stronger than his father. This is the legend of upper moon zero the son of Muzan.