"Koi Suru 1/4" is a manga series that explores themes of love, identity, and self-discovery through the lens of a unique romantic premise. The story centers around Aoi, a high school student who discovers that she is one-fourth vampire. This revelation comes to light when she meets her estranged grandfather, a full-blooded vampire, who explains her mixed heritage. Aoi’s life takes a dramatic turn as she grapples with her newfound identity and the challenges it brings, including heightened senses, a craving for blood, and the need to conceal her true nature from her peers.

Aoi’s world becomes further complicated when she develops feelings for her classmate, Ren, a kind and empathetic boy who is unaware of her vampiric lineage. Their budding romance is fraught with tension as Aoi struggles to balance her human emotions with her vampiric instincts. The narrative delves into the complexities of their relationship, exploring how Aoi’s dual nature affects her ability to connect with others and her own sense of self. Ren, on the other hand, must navigate his feelings for Aoi while sensing that she is hiding something significant.

The series also introduces other key characters, including Aoi’s grandfather, who serves as both a mentor and a reminder of the vampiric world she is tied to. His presence adds depth to the story, providing insight into the history and culture of vampires while challenging Aoi to reconcile her human and vampiric sides. Additionally, Aoi’s human friends and classmates play supporting roles, offering moments of levity and normalcy amidst the supernatural elements of the plot.

As the story progresses, Aoi faces various challenges, including threats from other vampires who view her mixed heritage as a threat to their kind. These conflicts force her to confront her identity and make difficult choices about where she belongs. The series balances its romantic elements with action and suspense, creating a dynamic narrative that keeps readers engaged. Through Aoi’s journey, "Koi Suru 1/4" examines themes of acceptance, the struggle between two worlds, and the power of love to transcend boundaries.