The Abysmal Flower presents a tragic romance narrative. The protagonist, Sylvia Pedelian, is central to a gory and erotic reverse harem plot concerning her revenge for her brother Cassis's disappearance. When a Korean student suddenly awakens in the novel's world, she realizes she has become the ill-fated Roxana—the villainous daughter of the Agreces, the Pedelians' sworn enemies. Since her father, Lante, is the one who captures and abuses Cassis, Roxana devises a plan fitting her family's wicked reputation to save Cassis and, by extension, herself. The Agrece castle is an unforgiving domain of betrayal, violence, and bloodshed. Over the years, Roxana has observed her father and half-siblings commit unspeakable atrocities, waiting for the day she could finally meet the shackled and battered Cassis. After Roxana displays rare interest in personally torturing and disciplining a prisoner, she is granted the chance to secretly nurse the apprehensive Cassis back to health. Witnessing the lengths Roxana goes to for his sake—at the cost of her own physical and mental wellbeing—Cassis resolves to one day return the favor.