In the latter half of the 21st century, humanity faced existential crises on Earth and launched a massive campaign of space colonization. About a hundred years later, a new threat emerged in the depths of space in the form of mysterious, gigantic creatures known as Star Beasts. To combat these monsters, humanity developed massive robotic armors called A.I.G.I.S. The pilots who risk their lives to defend the space colonies are celebrated as true heroes by the people.

The story begins by focusing on Ryu Tyler, an ordinary factory worker building A.I.G.I.S. units. He is a single father who lives happily with his young son, Leo, though their life is modest. While Ryu works a blue-collar job, his son Leo is a prodigy who wins VR mecha piloting championships, demonstrating incredible natural talent. Ryu wishes he could be a better role model for his son. His chance arrives unexpectedly when the Hero Organization, the official institution that manages hero pilots, personally invites him to become a civilian A.I.G.I.S. pilot. Determined to become a worthy hero in his son's eyes, Ryu accepts.

This initial premise is deceptive. Shortly after joining, Ryu discovers the dark truth about the Hero Organization. He learns that civilian pilots like him are treated as expendable cannon fodder, exploited as propaganda tools by those in power. Before he can act on this knowledge, Ryu is betrayed and murdered by his superiors, who stage his death to create an inspirational martyr for the public to rally behind.

The true protagonist is revealed to be his son, Leonidas Tyler, known as Leo. Eight years after his father's murder, Leo, now a teenager, enlists in the Hero Organization. He possesses his father’s determination and his own exceptional piloting skills. However, his goal is not to become a celebrated hero. Leo joins to infiltrate the organization from within, uncover the conspiracy behind his father’s death, and exact revenge on the people responsible[2][4][5][6]. The series shifts from the story of an ordinary man becoming a hero to a darker tale of vengeance and systemic corruption.

The conflict is not truly humanity versus the Star Beasts, which serve as a greater-scope threat, but a human versus human struggle. The Hero Organization represents a corrupt military-industrial complex that manufactures heroes as disposable symbols to manipulate the masses. Leo's mission is to expose the ugly, hypocritical reality hidden behind the glamorous facade of heroism and hold the true villains accountable. The manga explores central themes of heroism, how it can be used for both good and bad purposes, and how the pursuit of this ideal can lead to exploitation.

Major narrative arcs include the introductory arc following Ryu's recruitment and shocking death, followed by the main storyline focusing on Leo's training and secret agenda as he rises through the ranks of the organization that murdered his father. The series is set in a science fiction world of space colonies, giant mecha called A.I.G.I.S., and the mysterious Star Beasts that lurk in the cosmos.