"Akikan!" is a manga series that blends comedy, romance, and science fiction, centered around the concept of anthropomorphized beverage cans. The story begins when high school student Kakeru Daichi purchases a melon soda can from a vending machine, only to discover that it transforms into a humanoid girl named Melon. This transformation is the result of a secret government experiment aimed at creating "Akikans"—aluminum cans that can turn into human-like beings when filled with a specific type of carbonated drink. These Akikans are designed to test the durability of different types of aluminum alloys in combat scenarios.

Melon, along with other Akikans like Yogurt, a yogurt drink can, and Aoi, a juice can, becomes part of Kakeru's daily life. The Akikans are not only capable of human speech and emotions but also possess unique abilities tied to their beverage types. However, their existence is not without conflict. The Akikans are pitted against each other in battles to determine which alloy is superior, with the losing Akikan at risk of being discarded or recycled. Kakeru, despite his initial reluctance, becomes deeply involved in these battles as he strives to protect Melon and the other Akikans.

The narrative explores themes of coexistence, identity, and the ethical implications of creating sentient beings for experimental purposes. Kakeru's relationships with the Akikans, particularly Melon, evolve as he grapples with their humanity and the moral dilemmas surrounding their existence. The series also incorporates humor and lighthearted moments, often stemming from the absurdity of the premise and the interactions between the human characters and the Akikans.

As the story progresses, Kakeru and the Akikans face various challenges, including rival Akikans, government interference, and the broader implications of the Akikan project. The series balances its comedic and action-oriented elements with moments of introspection, particularly as the Akikans question their purpose and seek to define their own identities beyond their roles in the experiment. The manga concludes with a resolution that addresses the fate of the Akikans and their relationships with the human characters, leaving room for both closure and contemplation.