Sis-con Demon Lord

The big brother who will do everything just to be with his little sister even they're separated by different world. Yuuki who's Father got remarried and became a brother of three girls. His step-mother who was pregnant of his father child gave birth to his little sister and he became a protective big brother. This is a story of a big brother who was sent to another world and became demon lord, then returned back quickly to his home world just to be with his little sister after his world domination. (I'm still molding the idea. I'll will change the synopsis in the future.). --Geraint124x