Mr Katō--a curmudgeon and recent retiree--finds his only solace during his daily walks, where he wonders how his life went wrong and daydreams about getting a dog (which his wife won't allow). During one of these walks, he is approached by a young woman. She calls herself Mie, and invites him to join her business Happy Family, where employees act as part-time relatives or acquaintances for clients in need, for whatever reason, if only for a day.

At first reluctant, but then intrigued, he takes the job without telling his wife or adult children. Through the many roles he takes on, Mr Katō rediscovers the excitement and spontaneity of life, and re-examines his role in his own family. Using lessons learned with his "play families," he strives to reconnect with his loved ones, to become the father and husband they deserve, and to live the life he's always wanted.