Demon King? the Old Girl Is in Control!

Everything that has a good side must have a negative side. So—— The male protagonist travels to an unknown world with a pair of underwear at the beginning. After seeing this, do you think that this is a story about a wretched male protagonist who reaches the top of the world? Here, a certain protagonist takes a mortal body and becomes a demon. He becomes strong all the way and becomes a demon king. I once stepped on the gods with my feet, held the stars in my hands, and my consciousness and the abyss, all the demons and gods were just dust under my feet! Planets can collapse in the blink of an eye, and stars can form a river with just a drop of saliva! So what are you? Demon King! The old girl is in control! This is already abnormal! But my sister likes me, well, I would rather say she loves me deeply! An unknown sister: Get out! This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.