Yoshifumi Nitta, a mid-level yakuza, has his life permanently altered when a bizarre capsule crashes into his head. Although he assumes the odd incident was merely a dream, he discovers the capsule is still there the following morning; a young girl emerges from it. She recalls nothing except her name, Hina, and employs psychokinesis to force Yoshifumi to purchase clothes and toys for her. Unable to shake Hina, Yoshifumi is reluctantly forced into the role of her guardian. The duo's unusual existence is only just starting. While Hina lounges around the house, Yoshifumi rapidly ascends the yakuza hierarchy, aided by her supernatural powers. Hinamatsuri tracks this comedic pair as Hina drags both new friends and old acquaintances into her mischief, while Yoshifumi balances caring for Hina, concealing her abilities, and running yakuza operations.