"Kyōkenn Kareshi" centers on the relationship between a high school girl named Aoi and her childhood friend, Kakeru, who harbors a deep, obsessive love for her. Kakeru’s feelings are intense and possessive, often manifesting in controlling and manipulative behavior. Aoi, while aware of Kakeru’s overbearing nature, struggles with her own conflicting emotions, torn between her affection for him and her discomfort with his actions. The narrative explores the complexities of their bond, delving into themes of love, dependency, and emotional boundaries.

The story begins with Aoi and Kakeru reconnecting after years apart. Kakeru’s obsession with Aoi becomes immediately apparent as he inserts himself into her life, demanding her attention and affection. Despite his overprotectiveness, Aoi finds herself drawn to Kakeru’s unwavering devotion, even as his behavior grows increasingly erratic. Their relationship is further complicated by the presence of other characters, including Aoi’s friends and Kakeru’s rivals, who challenge the dynamics between the two.

As the plot progresses, Kakeru’s possessiveness escalates, leading to moments of tension and conflict. Aoi is forced to confront the darker aspects of their relationship, questioning whether Kakeru’s love is genuine or merely a reflection of his need to control her. The series examines the psychological impact of their interactions, highlighting the fine line between passion and obsession. Through its exploration of these themes, "Kyōkenn Kareshi" presents a nuanced portrayal of a relationship that is both compelling and unsettling, offering readers a thought-provoking look at the complexities of human emotions.