Rui Kamishiro is a self-employed genius alchemist. He lived in a kingdom whose ruler no one knew. And then, one day, Rui meets a beautiful girl in black... and falls in love. According to her, she was suffering from an illness, and Rui decided that he would cure her with his medicines and potions... that he would come up with something! But he didn’t know that he fell in love with a real princess...