The Abysmal Flower tells a tragic tale of romance. The heroine, Sylvia Pedelian, is at the heart of a gory and erotic reverse harem story about her revenge for the disappearance of her brother, Cassis. When a Korean student suddenly awakens in the world of the novel, she realizes she has become the ill-fated Roxana—a villainous daughter of the Agreces, the Pedelians' sworn enemies. As it is her father, Lante, who captures and abuses Cassis, Roxana devises a plan befitting the wickedness of her family name to save Cassis and, consequently, herself.

The Agrece castle is an unforgiving realm of betrayal, violence, and bloodshed. Over the years, Roxana has watched her father and half-siblings commit unspeakable atrocities, waiting for the day she can finally meet the shackled and battered Cassis. After Roxana shows rare interest in personally torturing and disciplining a prisoner, she is given the opportunity to secretly nurture the apprehensive Cassis back to health. Witnessing the lengths that Roxana goes to for his sake—at the expense of her own physical and mental wellbeing—Cassis resolves to one day return the favor.