The year is 1964. With Tokyo preparing to host the Olympics, buildings and highways are being constructed at a feverish pace, and excitement fills the air. Amidst all the change and commotion, the people of Third Street continue to carry on with their lives, as colorful and vibrant as ever.
The novelist Chagawa has married Hiromi, and the two now share a happy life with Junnosuke, the young boy he had taken in during the first film, who is now in high school. Chagawa continues to write his serial as the lead writer on the Adventure Boys Book magazine, but his popularity is threatened by a new writer.
Meanwhile, Norifumi Suzuki, his wife Tomoe, their only son Ippei and their live-in employee Mutsuko have gradually expanded their auto repair business, which has gotten an impressive makeover. But every morning, Mutsuko puts on makeup and steps out of her home — all so she can "happen to" run into and say hello to the young doctor, Kikuchi, who passes by on his way to work.
One day, Hiromi discovers a telegram that Chagawa had hidden. Who sent this telegram? What is the surprising identity of this new, rival writer? Will Mutsuko's affections be returned? And what future awaits the people of Third Street?