The film tells the story of young people who grew up around a 330-year-old fireworks factory that is about to be forcibly evicted. Keitarō has shut himself in the factory for four years to perfect the legendary "Shuhari" firework in place of his absent father. Meanwhile, his childhood friend Kaoru, who left her home due to an incident and has been living in Tokyo, visits Keitarō. In their reunion, the two hatch a surprising plan to find the secret of the long-lost firework.