Mukumi Nekoi is the older sister of Takumi Nekoi and the sole provider for the Nekoi household, working as an author in a dōjin group. Her income is vital as Takumi is a carefree NEET and their father struggles to hold stable employment. Though outwardly plain, Mukumi harbors a hidden side of her personality, unknown to others. The family lives in Nyagoya City, where cats are vanishing inexplicably. Mukumi becomes involved when their father gets a sudden job offer from Neko Kikaku, a company with ties to the phenomenon, prompting Takumi to act to save their father.