In the late 26th century, humanity faces a dire crisis as Earth's population surges and resources dwindle. To combat this, the United Nations initiates the Terraforming Project, aiming to colonize Mars by introducing algae and cockroaches to create a habitable environment. Centuries later, a mission is sent to Mars to assess the progress, but the crew discovers that the cockroaches have evolved into humanoid creatures called Terraformars, possessing immense strength, intelligence, and a violent hostility toward humans.

The story begins with the Annex I mission, a crew of genetically enhanced humans sent to Mars to eliminate the Terraformars and retrieve samples. Each member of the crew has been modified with the DNA of various organisms, granting them unique abilities to combat the Terraformars. However, the mission quickly turns disastrous as the crew is overwhelmed by the Terraformars' ferocity and numbers. The survivors return to Earth with critical information, but the mission is deemed a failure.

Subsequent missions, such as Annex II, follow with more advanced technology and stronger genetically modified individuals. These missions reveal deeper layers of the conflict, including political intrigue, corporate manipulation, and ethical dilemmas surrounding genetic engineering. The Terraformars are not merely mindless monsters; they exhibit signs of social structure and intelligence, raising questions about humanity's right to exterminate them.

Key characters include Akari Hizamaru, a stoic and skilled fighter with mantis DNA, and Michelle K. Davis, a determined leader with enhanced physical abilities. Other notable figures include Adolf Reinhard, a scientist with a mysterious agenda, and Shokichi Komachi, a former boxer with cockroach DNA, who struggles with his identity and humanity. The series explores their personal struggles, alliances, and betrayals as they navigate the brutal environment of Mars and the moral complexities of their mission.

The narrative delves into themes of survival, evolution, and the consequences of humanity's attempts to dominate nature. It also examines the darker aspects of human ambition, as factions on Earth exploit the crisis for power and profit. The Terraformars serve as both a physical threat and a symbolic challenge to humanity's hubris, forcing characters to confront their own limitations and the ethical implications of their actions.

As the story progresses, the conflict escalates, with humanity launching increasingly desperate missions to Mars while the Terraformars continue to evolve and adapt. The series balances intense action sequences with moments of introspection, creating a tense and thought-provoking narrative that explores the boundaries of science, morality, and survival.