Hikikomori (‘social withdrawal’) appeared in Japan at the end of the twentieth century, inciting public panic about a generation of Japanese youth who shun social contact and fail to engage in the age-appropriate activities of young adulthood. Widely cited as a ‘condition’ rather than a psychiatric symptom or disorder, hikikomori has functioned variously as a diagnosis of individuals, families, and society at large. Taking the polysemous (and controversial) nature of hikikomori as a starting point, we draw on fourteen months of ethnographic research to explore how families negotiate a diagnosis of hikikomori in everyday life. Our focus on families opens up fruitful questions about the moral economies of life under diagnosis, not simply for the diagnosed individual, but also for those who assume responsibility for that individual’s health and wellbeing.