Hayate Ayasaki, a 16-year-old boy, finds himself burdened with his parents' massive debt after they abandon him. Forced to work odd jobs to survive, Hayate becomes resourceful and skilled in various tasks, including combat and household chores. His life takes a dramatic turn when he attempts to kidnap Nagi Sanzenin, a wealthy young girl, to ransom her for money to pay off his debts. However, the plan backfires when Nagi misunderstands his intentions, believing he is confessing his love to her. Instead of turning him in, Nagi hires Hayate as her personal butler, offering to clear his debt in exchange for his services.

Nagi Sanzenin, the heiress to the vast Sanzenin fortune, is a sheltered and somewhat spoiled girl who lives in the luxurious Sanzenin mansion. Despite her wealth, she is lonely and struggles with social interactions. Hayate's arrival brings a new dynamic to her life, as he not only manages her household but also becomes her protector and confidant. The series explores their evolving relationship, blending comedy, romance, and action as Hayate navigates his new role and the challenges that come with it.

The narrative expands with the introduction of various supporting characters, each contributing to the series' comedic and dramatic elements. Maria, Nagi's maid and caretaker, serves as a stabilizing force in the household, often mediating between Hayate and Nagi. Klaus, the mansion's head butler, provides guidance to Hayate while maintaining the household's traditions. Other characters, such as Hinagiku Katsura, a skilled kendo practitioner and Nagi's friend, and Ayumu Nishizawa, Hayate's childhood friend, add layers to the story through their interactions and relationships with the main characters.

The series incorporates a mix of episodic and overarching storylines, often blending slice-of-life moments with more dramatic arcs. Hayate's past and the mystery surrounding his parents' disappearance are recurring themes, adding depth to his character. The narrative also delves into Nagi's family history, including her estranged relationship with her grandfather and the complexities of her inheritance. Supernatural elements, such as the Royal Garden and the Hakuou Academy's student council, introduce fantastical elements that contrast with the otherwise grounded setting.

Throughout the series, Hayate's unwavering dedication to his duties and his growing bond with Nagi form the emotional core of the story. The interplay between comedy and drama, along with the exploration of themes such as loyalty, friendship, and self-discovery, creates a multifaceted narrative that appeals to a wide audience. The series balances lighthearted moments with more serious undertones, ensuring a dynamic and engaging viewing experience.