What Kind of Death Should the Landlord Who Bullied the Great Demon King Choose?

After being saved by the angel Raphael, Lucifer transmigrates into a slave society and somehow becomes a major slave owner. To make matters worse, the younger sister he has always bullied turns out to be the future Demon King who will wreak havoc across the land. To avoid being killed and save his adorable imouto, Lucifer has no choice but to endure the pain and open that book, Five Years of College Entrance Exams and Three Years of Simulations...