Based on the plot of an award-winning Crayon Shin-chan animated movie from 2002, a boy named Shinichi (Takei) does the time-traveling and meets a feared general named Ijiri Matabei (Kusanagi). Ijiri is in love with Princess Ren (Aragaki) who subsequently rejects an arranged marriage to Okura Itakatora (Osawa), a powerful daimyo of northern Kanto. Enraged by the rejection, Okura sends a large army to Ijiri's smaller state and it's up to Shinichi to change their destiny.
