When bachelor Daikichi Kawachi attends his grandfather's funeral, he is surprised to find a mysterious young girl alone in the garden. To his astonishment, the shy and reserved girl, named Rin Kaga, is believed to be the illegitimate child of his late grandfather. Due to the shameful circumstances related to the little girl, no one in the family is willing to take her in following her father's death. Infuriated by the coldness extended to an innocent child, Daikichi announces that he will take care of Rin himself, despite his young age, single status, and lack of parental experience. Usagi Drop follows the story of Daikichi and Rin as they try to find happiness and purpose to their fateful meeting.