"L.A.G. Complex" is a science fiction manga series set in a dystopian future where humanity faces extinction due to a mysterious phenomenon known as the "L.A.G." (Life Altering Gene). This gene causes individuals to mutate unpredictably, leading to widespread chaos and societal collapse. The story centers on a group of genetically engineered soldiers called "Complexes," created to combat the L.A.G. outbreak and restore order. These soldiers possess enhanced abilities and are designed to resist the gene's effects, but they also struggle with their own humanity and the ethical implications of their existence.

The protagonist, Ryo Narushima, is a Complex who becomes a key figure in the fight against the L.A.G. outbreak. Ryo's journey is marked by internal conflict as he grapples with his identity, the purpose of his creation, and the moral dilemmas of using genetically engineered beings as tools of war. Alongside Ryo, other Complexes, such as the stoic and disciplined Aya Kisaragi and the enigmatic and rebellious Kaito Shiba, play pivotal roles in the narrative. Each character brings unique perspectives and abilities to the group, highlighting the diversity of their engineered traits and the complexities of their relationships.

The plot unfolds as the Complexes are deployed to various hotspots affected by the L.A.G. outbreak, encountering mutated humans, rogue factions, and government conspiracies. The series explores themes of survival, identity, and the consequences of genetic manipulation, as the characters navigate a world where the line between human and monster becomes increasingly blurred. Tensions rise as the Complexes uncover hidden truths about their origins and the true nature of the L.A.G. phenomenon, leading to confrontations with powerful adversaries and difficult choices that challenge their loyalty and resolve.

As the story progresses, the narrative delves into the broader implications of humanity's reliance on genetic engineering and the ethical boundaries of scientific advancement. The Complexes must confront not only external threats but also their own inner struggles, as they question their purpose and fight for a future where humanity and engineered beings can coexist. The series combines action, drama, and philosophical inquiry, creating a compelling exploration of a world on the brink of collapse and the individuals striving to save it.