"Hennako-chan" centers on the life of a young girl named Hennako, who discovers she possesses a unique ability to communicate with inanimate objects. This power, initially a source of confusion and fear, becomes integral to her daily life as she navigates the challenges of adolescence. The narrative unfolds in a small, rural town where Hennako lives with her grandmother, a wise and supportive figure who helps her understand and harness her gift. The story explores Hennako's interactions with various objects, each imbued with distinct personalities and histories, revealing their perspectives on the world and their relationships with humans.

The plot is driven by Hennako's journey of self-discovery and her efforts to balance her extraordinary ability with the ordinary struggles of school, friendships, and family. Key characters include her best friend, Taro, a skeptical yet loyal companion who often provides a grounded perspective, and her classmate, Yumi, whose curiosity about Hennako's abilities leads to both comedic and poignant moments. The series also introduces a mysterious antique shop owner, Mr. Kuroda, who becomes a mentor figure, offering insights into the origins of Hennako's power and its connection to the town's history.

As the story progresses, Hennako's ability attracts the attention of both allies and adversaries. A subplot involves a rival group seeking to exploit her power for their own gain, leading to conflicts that test Hennako's resolve and moral compass. The narrative balances lighthearted, slice-of-life moments with deeper themes of identity, responsibility, and the interconnectedness of all things. Through her interactions with the objects and the people around her, Hennako learns valuable lessons about empathy, courage, and the importance of understanding different perspectives. The series concludes with Hennako embracing her role as a bridge between the human and object worlds, leaving room for further exploration of her unique place in the universe.