"Atashi no Daiji Man" centers on the life of a young woman named Natsumi, who finds herself entangled in a series of unexpected and often comedic situations after encountering a mysterious man who claims to be her "guardian angel." This man, who introduces himself as Daiji, possesses supernatural abilities and insists that his sole purpose is to protect Natsumi from harm. Despite his seemingly noble intentions, Daiji's presence complicates Natsumi's life, as his over-the-top methods of safeguarding her often lead to chaos and misunderstandings.

The narrative explores Natsumi's struggle to balance her ordinary life with the extraordinary circumstances brought on by Daiji's interventions. As the story progresses, it becomes clear that Daiji's role as a guardian is tied to a deeper, more complex history involving Natsumi's past, which she has little memory of. This past gradually unravels through a series of flashbacks and revelations, revealing connections between Natsumi, Daiji, and a larger supernatural conflict.

Key characters include Natsumi, a pragmatic and somewhat skeptical individual who initially resists Daiji's presence but gradually comes to rely on him; Daiji, whose flamboyant and eccentric personality masks a genuine sense of duty and care for Natsumi; and a supporting cast of friends, rivals, and antagonists who contribute to the unfolding drama. The interactions between these characters drive the plot forward, blending humor, romance, and moments of tension as Natsumi navigates her dual reality.

The manga balances episodic comedic scenarios with an overarching narrative that delves into themes of trust, identity, and the consequences of past actions. As Natsumi and Daiji grow closer, their relationship evolves from one of reluctant dependence to mutual understanding, with both characters confronting their own vulnerabilities and the challenges posed by their intertwined fates. The story maintains a lighthearted tone while gradually introducing darker elements, creating a dynamic and engaging narrative.