After mysteriously being sent back in time, Shin-chan saves the life of Matabei Yoshitoshi Ijiri, a samurai who leads the army of a small province in Japan. Welcomed as a guest by Ijiri, Shinnosuke must figure out why he is stuck in 1574.

When a new threat regresses the minds of the adults of Kasukabe back into children, its up to Shinnosuke and his friends to reclaim their parents from becoming trapped in the nostalgia of the 20th Century.