"Sue-chan wa Himitsu" centers on Sue, a young girl who harbors a significant secret: she is a robot created by her father, a brilliant scientist. Despite her mechanical nature, Sue lives a seemingly ordinary life, attending school and forming friendships, all while concealing her true identity from those around her. The narrative explores the challenges she faces in maintaining this secret, particularly as she grows closer to her classmates and experiences the complexities of human emotions.

The story delves into Sue's internal conflict as she grapples with her dual identity. On one hand, she strives to blend in and experience life as a human, forming bonds with her peers and navigating the typical trials of adolescence. On the other hand, she must constantly be vigilant to avoid revealing her robotic nature, which could lead to social ostracism or even danger. This tension is a recurring theme, as Sue's actions and decisions are often influenced by her need to protect her secret while still pursuing her desire for genuine human connection.

Key characters include Sue's father, who serves as both her creator and primary caretaker. His role is pivotal, as he not only provides the technological expertise that allows Sue to function but also offers emotional support and guidance as she navigates her unique circumstances. Sue's classmates and friends also play significant roles, as their interactions with her highlight the contrast between her robotic nature and her human-like behavior. These relationships are central to the narrative, as they drive much of the emotional and situational conflict.

The plot is structured around episodic encounters that test Sue's ability to maintain her secret while also exploring themes of identity, belonging, and the nature of humanity. Each chapter typically presents a new challenge or scenario that forces Sue to confront her limitations and the ethical implications of her existence. These situations range from mundane school activities to more dramatic events, all of which serve to deepen the reader's understanding of Sue's character and the world she inhabits.

Overall, "Sue-chan wa Himitsu" is a thoughtful exploration of what it means to be human, told through the lens of a robot striving to live a normal life. The series balances lighthearted moments with more serious reflections on identity and acceptance, creating a narrative that is both engaging and thought-provoking.