Schoolgirl Rumiako has always cherished the fairy tale "Rubynight" as her favorite book. One day, the spider monster Spander emerges from its pages, possesses her brother's body, and plots to conquer the human world. To stop Spander's scheme, Rubynight herself steps out of the book and lends her body to Rumiako, who rises to fight. Spander sends minions to attack Rubynight, but Rumiako's fencing skills gradually corner them, ultimately making it possible to defeat Spander. However, this victory comes at a terrible cost—Rumiako faces the tragic dilemma of losing her brother's life. Amid this crisis, the story reaches a climax filled with love and hope.