The genius boy who is scheduled to become the [Last Boss Demon King] loves me, who has been reincarnated as a fairy. One day, Louis, a young boy with a talent that surpasses adults as a court magician, and his sickly sister, catch a fairy in the forest. It was Eleanor, a girl who was reincarnated into another world as a fairy on the side of the hero in this maiden game. Her palm-sized girlfriend lives in a cage. However, by drinking Louis' blood, he was able to change to the size of a human woman...? Louis pours out a sick love for Eleanor. What is the true purpose of this handsome and promising man in this world? A fantasy romance between a fairy girl and a frighteningly beautiful boy Demon King!