"Bullet/Bullet" is a science fiction anime series set in a dystopian future where humanity is on the brink of collapse due to a mysterious phenomenon known as the "Collapse Wave." This catastrophic event has caused widespread destruction, rendering much of the planet uninhabitable and forcing survivors into isolated city-states. The story centers on a young protagonist named Rei, a skilled marksman and former soldier, who becomes entangled in a high-stakes mission to uncover the truth behind the Collapse Wave and its origins.

Rei is recruited by a clandestine organization known as the "Bullet Corps," a group of elite operatives tasked with investigating and neutralizing threats related to the Collapse Wave. The Corps operates under the leadership of Commander Aya, a enigmatic and calculating figure with her own hidden agenda. Rei is paired with a genetically engineered combat partner named Lina, who possesses enhanced physical abilities and a mysterious connection to the Collapse Wave. Together, they embark on a series of missions that take them across the desolate wastelands and into the heart of the collapsing world.

As the story progresses, Rei and Lina uncover fragments of a larger conspiracy involving a shadowy corporation called NovaTech, which appears to have played a pivotal role in the Collapse Wave's emergence. The corporation's experiments with advanced technology and artificial intelligence have inadvertently triggered the disaster, and its leaders are now attempting to exploit the chaos to consolidate power. The duo faces numerous adversaries, including rogue AI constructs, mercenaries, and rival factions vying for control of the remaining resources.

The narrative explores themes of survival, loyalty, and the ethical implications of technological advancement. Rei's internal struggle with his past and his growing bond with Lina add emotional depth to the story, while the series maintains a steady pace with its action-driven plot and intricate world-building. The anime balances intense combat sequences with moments of introspection, as the characters grapple with the moral ambiguities of their mission and the uncertain future of humanity.

By the series' conclusion, Rei and Lina confront the architects of the Collapse Wave, leading to a climactic showdown that determines the fate of the world. The resolution leaves room for interpretation, with lingering questions about the true nature of the Collapse Wave and the potential for humanity's redemption. "Bullet/Bullet" offers a compelling blend of science fiction, action, and character-driven drama, making it a notable entry in the genre.