"Kuro ga Ita Natsu" is a poignant coming-of-age story set in a small Japanese town during the summer of 1966. The narrative centers on Natsu, a high school girl who lives with her mother and younger sister after the death of her father. Her life takes an unexpected turn when she encounters a mysterious boy named Kurosaki, who has recently moved to the town. Kurosaki is quiet, aloof, and carries an air of melancholy, which intrigues Natsu and draws her closer to him.

As Natsu and Kurosaki spend more time together, their relationship deepens, and Natsu begins to uncover the secrets of Kurosaki's past. It is revealed that Kurosaki is not an ordinary boy but a ghost, lingering in the human world due to unresolved emotions tied to his untimely death. Despite this revelation, Natsu remains determined to help Kurosaki find peace, even as their bond grows stronger and more emotionally complex.

The story explores themes of loss, grief, and the fleeting nature of life, as Natsu grapples with her own feelings of loneliness and the weight of Kurosaki's tragic circumstances. The summer setting serves as a backdrop for their interactions, emphasizing the transient beauty of the season and mirroring the impermanence of their connection. Supporting characters, such as Natsu's friends and family, provide additional layers to the narrative, highlighting the impact of Kurosaki's presence on those around him.

The emotional core of the story lies in the delicate balance between Natsu's desire to hold onto Kurosaki and her understanding that he must eventually move on. The series culminates in a bittersweet resolution, as Natsu comes to terms with the inevitability of parting ways with someone she has grown to care for deeply. "Kuro ga Ita Natsu" is a heartfelt exploration of love, memory, and the enduring impact of human connections, even in the face of loss.