While continuing his writing and consulting on foreign affairs, Masuzoe relocated from Tokyo to Kitakyushu in the 1990s to take care of his aging mother, who began to show signs of deteriorating mental health. In 1998, he published a book entitled "When I Put a Diaper on My Mother", which details his experience caring for his mother and the obstacles imposed by the Japanese welfare system. The book sold 100,000 copies, more than any of his previous political works, and propelled Masuzoe into the national spotlight as an authority on the aging society in Japan.