Life isn't easy for Basara Toujou. As the elder step-brother to two devil sisters, Mio and Maria Naruse, he has the responsibility of safeguarding them from covetous demons who aim to exploit Mio's powers. Additionally, heightened political unrest within the demon realm heightens the complexity of his mission. Despite the danger, when a messenger delivers an invitation for Mio to visit the demon domain, she and her companions embark on the journey. Now treading on hostile land, Basara must acquire greater strength through sensual gratification to achieve the unthinkable - protect everyone.