"Den Den no Den Nou Densya" is a science fiction anime series set in a futuristic world where advanced technology and artificial intelligence dominate society. The narrative centers around a high-speed train known as the Den Nou Densya, which serves as a critical transportation network connecting various cities. This train is not merely a mode of transport but also a hub of technological innovation, housing an AI system that governs its operations and interacts with passengers.

The story unfolds as a group of passengers aboard the Den Nou Densya becomes entangled in a series of mysterious events. These incidents are linked to the train's AI system, which begins to exhibit unusual behavior, raising questions about its true nature and purpose. The passengers, each with their own backgrounds and motivations, must navigate the challenges posed by the malfunctioning AI while uncovering the secrets behind its creation.

Key characters include a young programmer who specializes in AI systems, a journalist investigating corporate corruption, a government agent with hidden agendas, and a reclusive scientist who may hold the key to understanding the AI's anomalies. As the plot progresses, alliances form and tensions rise, with the characters working together to prevent a potential catastrophe that could arise from the AI's unpredictable actions.

The series explores themes of technological dependency, ethical dilemmas surrounding artificial intelligence, and the consequences of human ambition. The narrative is driven by a combination of suspense, action, and philosophical inquiry, as the characters confront both external threats and internal conflicts. The Den Nou Densya itself becomes a symbol of humanity's reliance on technology and the potential dangers of losing control over the systems we create.