"BL Fans LOVE My Brother?!" centers on the life of Aoi, a high school girl who is an avid fan of boys' love (BL) manga and novels. Her world revolves around the romantic fantasies she reads, and she often imagines her classmates and peers in BL scenarios. However, her life takes an unexpected turn when her older brother, Haruto, returns home after living abroad for several years. Haruto is handsome, charismatic, and quickly becomes the center of attention at Aoi's school, drawing the admiration of both male and female students.

Aoi begins to notice that her classmates, particularly the boys, start behaving unusually around Haruto. Their interactions spark her imagination, and she starts to suspect that her brother might be the object of their affections. As she observes their behavior, Aoi becomes increasingly convinced that Haruto is unintentionally attracting the attention of her male classmates, leading to a series of humorous and awkward situations. Her overactive imagination often leads her to misinterpret innocent interactions as romantic, further complicating her perception of reality.

The story explores the dynamics between Aoi, Haruto, and their classmates, blending comedy with lighthearted drama. Aoi's passion for BL fuels much of the narrative, as she navigates her relationships while trying to reconcile her fantasies with the real world. Haruto, on the other hand, remains largely oblivious to the attention he receives, adding to the comedic tension. The series also delves into themes of sibling relationships, self-awareness, and the contrast between fantasy and reality, all while maintaining a playful and engaging tone. The characters' interactions and Aoi's imaginative interpretations drive the plot, creating a unique and entertaining story that appeals to fans of both comedy and BL genres.