"Plastic Memories" is set in a near-future world where advanced androids, known as Giftia, are integrated into society as companions and workers. These androids have a limited lifespan of approximately nine years and four months before their memories degrade, rendering them unstable. To manage this, the Terminal Service Department of the SAI Corporation is tasked with retrieving and decommissioning Giftia before they become hazardous.

The protagonist, Tsukasa Mizugaki, joins the Terminal Service Department after failing his college entrance exams. He is paired with Isla, a skilled Giftia who works as a retrieval partner. Despite her expertise, Isla struggles with her own impending expiration date, which creates a poignant dynamic between the two. As they work together to retrieve Giftia from their owners, the series explores themes of loss, memory, and the transient nature of relationships.

The narrative unfolds through episodic cases, each focusing on different Giftia and their owners, highlighting the emotional bonds formed between humans and androids. These cases often culminate in bittersweet farewells, emphasizing the inevitability of separation. Central to the story is the evolving relationship between Tsukasa and Isla, which deepens as they confront the reality of her limited lifespan. Their partnership is marked by moments of humor, tenderness, and introspection, as Tsukasa grapples with his feelings for Isla and the ethical implications of their work.

Supporting characters include Michiru Kinushima, a cheerful and energetic colleague, and Kazuki Kuwanomi, the stern but caring supervisor of the Terminal Service Department. Each character contributes to the exploration of the series' central themes, providing additional perspectives on the human-android dynamic. The story builds toward a climactic resolution as Tsukasa and Isla face the inevitable conclusion of their time together, culminating in a poignant and emotionally resonant finale. "Plastic Memories" balances its episodic structure with a cohesive narrative arc, offering a thoughtful examination of love, memory, and the passage of time.