A brilliant but unhinged scientist once cultivated a unique flower in his pursuit of eternal youth and immortality, embedding the seeds of this "Premier Rose" within human beings. Carrying roses inside their bodies bestowed upon the human hosts not only various advantages but also several side effects, including the roses' requirement to feed on victims. Most of the test subjects, known as "Black Roses," were utilized as living weapons and kept under the control of their creator. One experimental subject was labeled a "defective failure" and concealed away. Claudia, the "Rose Witch," also referred to as a "Crimson Rose," typically does not need to feed on humans and only does so when she loses her self-control. When the Roses' creator vanished five years ago, the organization conducting the research quickly rebranded itself as "Red Rose." Brought out of the shadows, Claudia became Red Rose's primary method for eliminating the suddenly uncontrollable Black Roses. Protected by Wilhelm, the "Thorn," who shares a blood covenant with her—and collaborating with a special division of Red Rose called "Crimson-Shell"—Claudia must survive betrayal by a suspected traitor within the organization, as well as uncover the truth behind a "Jet Rose" who may be leading the Black Roses.