Watch Crayon Shin-chan: Unkokusai no Yabou - Full movie

A member of the Time Patrol finds out that there is a disturbance in Japan, 1570. While heading to that particular time and location to investigate, she is attacked and ends up stuck underground the Nohara residence at the end of the 20th century Japan. Having limited resources at hand, she is forced to ask for the help of the Nohara family. Together they go back in time and meet with a samurai named Fubuki-maru who believes that they are the legendary three persons and dog whom someone from her family would eventually meet in a crucial moment. The lonely samurai asks for their assistance in defeating the man that possesses strange magical powers, the sinister Unkokusai lord.

(Source: Anime News Network)