"Sex Hypnotist Zero" is a psychological and supernatural anime series that explores themes of control, desire, and morality. The narrative centers on a young man named Rei, who discovers he possesses an unusual ability: the power to hypnotize others into fulfilling their deepest, often repressed, desires. This ability manifests after a mysterious encounter with a shadowy figure, who grants Rei the power in exchange for an unspecified future favor. As Rei begins to experiment with his newfound skill, he quickly realizes the ethical dilemmas and consequences that come with manipulating the wills of others.

The story unfolds in a modern urban setting, where Rei navigates his dual life as a college student and an increasingly influential figure in the lives of those he hypnotizes. His ability attracts the attention of various individuals, including a secretive organization that seeks to exploit his powers for their own agenda. This organization, led by a enigmatic woman named Aya, views Rei as a potential tool to achieve their goals, which involve reshaping societal norms and controlling key figures in politics and business.

Rei's relationships with the people around him become increasingly complex as he struggles with the moral implications of his actions. His childhood friend, Yuki, becomes suspicious of his behavior, while a fellow student, Haruto, becomes an unwitting pawn in Rei's experiments. As Rei delves deeper into the world of hypnosis, he encounters others with similar abilities, leading to confrontations that challenge his understanding of power and responsibility.

The series delves into the psychological effects of Rei's actions on both himself and his subjects. Characters who fall under his influence experience a range of emotions, from euphoria to deep regret, as their suppressed desires are brought to the surface. The narrative also explores the darker aspects of human nature, such as manipulation, obsession, and the consequences of unchecked power.

As the story progresses, Rei is forced to confront the true nature of his ability and the intentions of those who seek to control him. The shadowy figure who granted him his power begins to reveal their own motives, leading to a climactic confrontation that tests Rei's resolve and forces him to make difficult choices about his future. The series concludes with an open-ended resolution, leaving room for interpretation regarding Rei's ultimate fate and the broader implications of his actions.