"Hime 100%" centers around a high school student named Hime, who is known for her striking beauty and aloof demeanor. Despite her popularity, Hime maintains a distant and cold attitude toward her peers, earning her the nickname "Ice Princess." The story takes a turn when a classmate, Akira, discovers a peculiar secret about Hime: she possesses a unique ability to transform into a completely different personality when her stress levels reach 100%. This alternate persona, known as "Himeko," is cheerful, outgoing, and entirely unlike her usual self.

Akira, intrigued by this duality, becomes determined to uncover the reasons behind Hime's transformation and help her reconcile her two identities. As the narrative progresses, it delves into Hime's past, revealing the emotional trauma and societal pressures that led to the creation of her alternate personality. The series explores themes of identity, self-acceptance, and the impact of external expectations on personal growth.

The dynamic between Hime and Akira evolves as they navigate the challenges of high school life, relationships, and personal struggles. Supporting characters, including classmates and family members, play significant roles in shaping the story, adding depth to the central conflict. The manga balances moments of humor and lightheartedness with more serious explorations of mental health and emotional resilience.

As Hime gradually confronts her fears and insecurities, the story emphasizes the importance of understanding and embracing one's true self. The interplay between Hime's dual personas serves as a metaphor for the complexities of human emotions and the journey toward self-discovery. The narrative concludes with a resolution that underscores the value of genuine connections and the courage to face one's inner struggles.