"Princess Principal" is set in an alternate steampunk-inspired version of 19th-century London, where the city is divided into two warring factions: the Kingdom of Albion and the Commonwealth. The story unfolds in a politically charged environment, with espionage and intrigue at its core. The narrative centers on a group of five young female spies attending Queen’s Mayfair, a prestigious girls' school, while operating undercover for the Commonwealth. Each member of the team possesses unique skills, and their missions often involve high-stakes infiltration, sabotage, and intelligence gathering.

The protagonist, Ange le Carré, is a skilled spy with a mysterious past, posing as a transfer student. Her partner, Princess Charlotte, is the heir to the Albion throne but secretly supports the Commonwealth’s cause. Dorothy, the team’s sharpshooter and strategist, provides tactical expertise, while Beatrice, a former actress, uses her talents for disguise and deception. Chise, a samurai from Japan, contributes her combat prowess and loyalty. Together, they navigate a web of political conspiracies, personal conflicts, and moral dilemmas as they carry out covert operations.

The series employs a non-linear narrative structure, with episodes often jumping between past and present to reveal character backstories and the evolution of their relationships. Key themes include loyalty, identity, and the blurred lines between right and wrong in a world dominated by espionage. The missions range from retrieving sensitive documents to thwarting assassination plots, each contributing to the overarching tension between Albion and the Commonwealth. The characters’ personal struggles and motivations are interwoven with the larger political conflict, adding depth to the story.

"Princess Principal" balances action-packed sequences with moments of introspection, exploring the emotional toll of espionage on its characters. The series concludes with an open-ended resolution, leaving room for interpretation while tying together key narrative threads. The interplay between the characters’ dual lives as students and spies, combined with the richly detailed steampunk setting, creates a compelling and immersive narrative.