"Koyamasō no Kiraware Mono" centers around the residents of Koyama Apartments, a rundown building inhabited by individuals who are ostracized or disliked by society. The story explores their daily lives, interactions, and the reasons behind their social alienation. Each character carries a unique backstory that contributes to their current status as outcasts, and the narrative delves into their struggles, relationships, and personal growth.

The protagonist, Koyama, is the landlord of the apartment complex. Despite his gruff and unapproachable demeanor, he harbors a deep sense of responsibility toward his tenants. His past is shrouded in mystery, but it becomes evident that he has faced significant hardships, which have shaped his worldview and his commitment to providing a refuge for others who are similarly marginalized.

Among the tenants is a former idol who was driven out of the entertainment industry due to a scandal, a reclusive artist with a troubled past, a man falsely accused of a crime, and a young woman ostracized for her unconventional lifestyle. Each character’s story is interwoven with the others, creating a tapestry of interconnected lives. The narrative often shifts focus between their individual arcs, revealing how their experiences and choices have led them to Koyama Apartments.

The series balances moments of humor, drama, and introspection, highlighting the complexities of human relationships and societal judgment. Themes of redemption, acceptance, and the search for belonging are central to the story. The interactions between the characters often lead to unexpected alliances and personal revelations, as they navigate their shared environment and confront their pasts.

As the story progresses, the residents of Koyama Apartments gradually form a makeshift family, finding solace and understanding in one another despite their differences. The series does not shy away from depicting the harsh realities of their lives, but it also emphasizes the resilience and humanity of its characters. Through their collective journey, "Koyamasō no Kiraware Mono" offers a poignant exploration of what it means to be an outcast and the possibility of finding connection in unlikely places.