"Sukeban Deka" centers on Saki Asamiya, a teenage girl who becomes an undercover agent for a secret government organization. After being released from juvenile detention, Saki is recruited to infiltrate high schools and dismantle criminal organizations operating within them. Her weapon of choice is a yo-yo, which she wields with exceptional skill, using it both as a tool for combat and investigation. The series blends elements of action, mystery, and drama, with a focus on Saki's dual identity as both a delinquent and a covert operative.

The narrative unfolds as Saki is assigned to various schools, each harboring its own criminal underworld. These criminal groups often involve corrupt teachers, student gangs, and external syndicates exploiting the school environment. Saki's missions require her to uncover the truth behind these organizations, often leading to intense confrontations and moral dilemmas. Her background as a former delinquent gives her insight into the mindset of her adversaries, but it also complicates her relationships with classmates and authority figures.

Supporting characters include Saki's handler, a mysterious figure who provides her with missions and guidance, and her classmates, who often become entangled in her investigations. The series explores themes of justice, loyalty, and the blurred lines between right and wrong, as Saki navigates the challenges of her dual role. Her journey is marked by personal growth, as she grapples with her past and the ethical implications of her actions.

The plot is episodic, with each arc focusing on a new school and its associated criminal activity, but overarching storylines tie the series together. These include Saki's quest to uncover the truth about her mother's death, which is linked to the criminal underworld she is tasked with dismantling. The series also delves into the broader conspiracy behind the government organization that employs her, raising questions about its true motives and methods.

"Sukeban Deka" is notable for its dynamic action sequences, intricate plotting, and exploration of social issues within the context of its high school settings. The character of Saki Asamiya stands out as a strong, complex protagonist, whose struggles and triumphs drive the narrative forward. The series has been adapted into multiple media formats, including live-action films and television dramas, reflecting its enduring popularity and cultural impact.