"Hinamatsuri" centers on the unexpected and chaotic relationship between Nitta Yoshifumi, a yakuza member, and Hina, a mysterious young girl with telekinetic powers. The story begins when Hina suddenly materializes in Nitta's apartment, disrupting his otherwise mundane life. Initially, Nitta is reluctant to care for her, but he quickly realizes her extraordinary abilities could be advantageous for his yakuza activities. However, Hina's unpredictable nature and lack of understanding of human norms lead to comedic and often heartwarming situations as Nitta attempts to balance his criminal lifestyle with the responsibilities of an impromptu guardian.

Hina's presence introduces a series of interconnected subplots involving other characters, such as Anzu, another telekinetic girl who ends up living with a homeless community after being abandoned by her handlers. Anzu's story contrasts with Hina's, as she learns to adapt to a life of hardship and forms bonds with the kind-hearted people around her. Meanwhile, Hitomi Mishima, a classmate of Hina's, becomes a central figure in the narrative. Despite being an ordinary middle school student, Hitomi's resourcefulness and work ethic lead her to take on multiple part-time jobs, often resulting in absurd and humorous scenarios.

The series explores themes of family, belonging, and personal growth through its diverse cast. Nitta evolves from a self-centered yakuza member to a more compassionate figure, while Hina gradually learns about human emotions and relationships. Anzu's journey highlights resilience and the importance of community, and Hitomi's experiences provide a satirical look at societal expectations and the pressures of adolescence. The interplay between the characters' supernatural abilities and their everyday struggles creates a unique blend of comedy, drama, and slice-of-life elements, making "Hinamatsuri" a multifaceted narrative that balances humor with heartfelt moments.