Japan currently displays many signs of a second demographic transition, which is marked by subreplacement fertility, a focus on self-fulfillment, and changes in family, residence, and marriage patterns. Concurrently, increased pet-keeping and related spending have occurred. The purpose of the current study was to determine whether the emergence of pet parenting can be documented in Japan. Previously documented in the United States and India, pet parenting is defined as the human investment of money, emotion, and time in companion animals that is like parental investment in children. We collected 615 online survey responses from pet owners (female = 48.1%, male = 51.9%; parents = 39.0%, nonparents = 35.8%, future parents = 25.2%). In addition to demographic questions about respondents and their companion animal, each completed the Lexington Attachment to Pets Scale (LAPS) and a series of questions regarding Affective Responsiveness, Training and Play, and General Care (collectively, CARES). Our results found clear, significant sex differences on all scales, including the total LAPS score, with women reporting more agreement on the attitudes or frequency of behaviors throughout. Nonparents and future parents reported significantly higher total LAPS scores, with the biggest difference compared with parents on the People Substituting scale. Nonparents were also found to report more frequent General Care and Affective Responsiveness on the CARES scales. We conclude that intuitive but novel differences in human-to-pet attachment and caregiving behavior demonstrate that pet-keeping practices can follow sex roles seen in parenting. Additionally, nonparents are more likely to invest in the direct care of companion animals in ways that mirror in adult-to-child parenting practices.