"Ore ga Suki nano wa Imōto dakedo Imōto ja nai" centers around Yuu Nagami, a high school student and aspiring light novel author who writes under the pen name Chikai Towano. Yuu’s stories often feature imouto (younger sister) characters, a trope he is particularly fond of. His younger sister, Suzuka Nagami, is a talented track athlete with a cold and aloof demeanor, often dismissing Yuu’s interests. Despite their strained relationship, Yuu’s life takes a turn when Suzuka discovers his secret career as a light novel author.

The plot intensifies when Suzuka, after reading Yuu’s work, accuses him of basing the protagonist’s sister on her. This misunderstanding leads to a series of comedic and dramatic interactions as Suzuka demands that Yuu prove his stories are not inspired by her. Meanwhile, Yuu’s editor, Ahegao Double Peace-sensei, pushes him to collaborate with an illustrator to enhance his work. This leads to the introduction of Minami Fuwa, a talented artist who becomes Yuu’s illustrator and a key figure in his life. Minami’s cheerful and eccentric personality contrasts sharply with Suzuka’s reserved nature, creating a dynamic and often chaotic trio.

As the story progresses, Yuu navigates the challenges of balancing his personal life, his relationship with Suzuka, and his professional aspirations. Suzuka’s initial disdain for Yuu’s work gradually softens, and she begins to take an interest in his creative process. The series explores themes of sibling relationships, creative expression, and the complexities of personal identity. Supporting characters, such as Yuu’s classmates and fellow authors, add depth to the narrative, contributing to both comedic moments and emotional arcs.

The manga blends slice-of-life elements with romantic comedy, often playing on the tropes of light novels and otaku culture. Yuu’s passion for writing and his interactions with Suzuka and Minami drive the story forward, creating a balance between humor and heartfelt moments. The series delves into the challenges of pursuing creative endeavors while maintaining personal relationships, offering a nuanced portrayal of its characters’ growth and struggles.