"Yoshinaga-san Chi no Gargoyle" centers on the life of Yoshinaga, a high school student who discovers a small, sentient gargoyle statue in his family's attic. The gargoyle, named Gee, possesses the ability to speak and exhibits a mischievous yet endearing personality. Despite its stone exterior, Gee is capable of movement and displays a range of emotions, often acting as a catalyst for comedic and heartwarming situations.

The narrative explores the dynamic between Yoshinaga and Gee as they navigate everyday life. Yoshinaga, initially reluctant to care for the gargoyle, gradually forms a bond with Gee, treating it as both a pet and a companion. The series delves into their interactions with Yoshinaga's family, friends, and classmates, who are often surprised or amused by Gee's presence. The gargoyle's antics frequently lead to humorous misunderstandings, but also serve to highlight themes of friendship, responsibility, and acceptance.

Secondary characters, such as Yoshinaga's younger sister and his classmates, play significant roles in the story, often reacting to Gee's peculiar nature or becoming involved in its escapades. The series balances slice-of-life elements with lighthearted fantasy, creating a narrative that is both grounded and whimsical. The episodic structure allows for a variety of scenarios, from school events to family outings, all of which are influenced by Gee's unique perspective and abilities.

The manga maintains a consistent tone of warmth and humor, with occasional moments of introspection as Yoshinaga reflects on his growing attachment to Gee. The gargoyle's origins and the reason for its sentience remain ambiguous, adding an element of mystery to the otherwise straightforward plot. Through its blend of comedy, fantasy, and everyday life, "Yoshinaga-san Chi no Gargoyle" offers a charming exploration of unconventional relationships and the unexpected joys they can bring.