In today's world, two individuals are born - the Maou (demon king) and the Yuusha (hero). According to the age-old belief, the hero must defeat the demon king both physically and mentally before he can conquer the world. However, this belief is no longer relevant, and the reborn demon king, Mao, doesn't take it seriously. Despite having exceptional powers that attract other evil characters, Mao has no desire to rule the world.
One day, Kamiko, the hero, enters Mao's workplace and recognizes him as the demon king. To test her theory, she kisses him. However, Mao wishes to continue his routine and get rid of Kamiko, but she seizes his company, making things complicated. From then on, their lives become intertwined, and Kamiko suggests that the only way to defeat Mao correctly is through sexual intercourse.
