"Kidō Senshi Gundam AGE: Hajimari no Monogatari" is a manga adaptation of the "Mobile Suit Gundam AGE" anime series, serving as a prequel that expands on the events leading up to the main storyline. The narrative is set in the Advanced Generation (A.G.) era, a distant future where humanity has colonized space but faces a relentless threat from the mysterious alien race known as the UE (Unknown Enemy). The story primarily focuses on the development of the Gundam AGE-1, a revolutionary mobile suit designed to combat the UE, and the early life of its creator, Flit Asuno.

The manga begins with Flit Asuno as a young boy living on the colony of Ovan. His life is upended when the UE launches a devastating attack, resulting in the destruction of his home and the death of his mother. This traumatic event becomes the catalyst for Flit's determination to protect humanity. Inheriting the "AGE Device," a mysterious artifact left by his mother, Flit begins to study its advanced technology, which contains the blueprints for the Gundam AGE-1. Over time, he develops into a brilliant engineer, driven by a desire to create a weapon capable of defending humanity from the UE.

As Flit grows older, he joins the Earth Federation Forces and becomes a key figure in the development of the Gundam AGE-1. The manga explores the challenges he faces in gaining support for his project, as well as the political and military tensions within the Earth Federation. The UE's attacks grow more frequent and devastating, forcing Flit to accelerate his work. The Gundam AGE-1 is eventually completed, and Flit takes on the role of its pilot, marking the beginning of humanity's counteroffensive against the UE.

The manga also introduces other significant characters, such as Emily Amonde, Flit's childhood friend and eventual love interest, who provides emotional support and plays a role in his journey. Additionally, the story touches on the broader conflict between humanity and the UE, hinting at the deeper mysteries surrounding the alien race's origins and motives. The narrative sets the stage for the events of the main "Mobile Suit Gundam AGE" series, providing context for Flit's lifelong mission and the legacy of the Gundam AGE-1.

Overall, "Kidō Senshi Gundam AGE: Hajimari no Monogatari" serves as a foundational piece that enriches the "Gundam AGE" universe by delving into the origins of its central protagonist and the creation of the iconic mobile suit. It balances personal drama with the larger-scale conflict, offering a compelling prelude to the main series.