The manga series "Rockman X4" adapts the events of the 1997 video game of the same name, set in the "Mega Man X" universe. The story unfolds in a futuristic world where humans and advanced humanoid robots, known as Reploids, coexist. The narrative centers on the Maverick Hunters, an organization tasked with combating rogue Reploids called Mavericks, who threaten the peace. The Maverick Hunters are led by Sigma, a former hero turned antagonist, who orchestrates a rebellion against humanity.

The plot begins with the sudden uprising of the Repliforce, a military organization of Reploids led by Colonel, who seeks independence from human control. The Repliforce is falsely accused of causing a catastrophic space colony crash, leading to widespread destruction and loss of life. This incident sparks a conflict between the Maverick Hunters and the Repliforce, with both sides believing they are fighting for justice. The story is told through the perspectives of two protagonists: X, an idealistic and compassionate Maverick Hunter, and Zero, a skilled and determined warrior with a mysterious past.

X, designed with a strong sense of justice, struggles with the moral implications of fighting fellow Reploids, questioning whether violence is the only solution. Zero, on the other hand, is more pragmatic and driven by a desire to uncover the truth behind the conflict. As the story progresses, both characters confront their own doubts and motivations while battling powerful Mavericks, including members of the Repliforce such as Colonel, Iris, and Double. The narrative explores themes of loyalty, identity, and the consequences of war, as X and Zero uncover the true mastermind behind the chaos: Sigma, who manipulates events to incite a war between humans and Reploids.

The climax of the story involves a series of intense battles, culminating in a confrontation with Sigma. X and Zero must overcome their differences and work together to stop Sigma's plan, which threatens to destroy both humans and Reploids. The resolution of the conflict leaves lasting impacts on the characters, particularly Zero, who faces personal loss and a deeper understanding of his purpose. The manga stays faithful to the game's narrative while expanding on character interactions and emotional depth, providing a cohesive and engaging adaptation of the source material.