The scene starts with a 30th century time patrol machine T2327X travelling through time. An anomaly occurs in Japan around 1570AD during the Sengoku period. The officer, suspecting it to be a crime, contacts the headquarters, but in vain. So, the officer decides to investigate the crime alone. Suddenly, the time machine meets with a mysterious space-time torpedo assault, and is forced to conduct an emergency landing. The emergency landing location is deep underground, in the backyard of the Nohara family’s house, under Shiro’s doghouse.
The officer takes control over Shiro’s body and tells the Nohara family about disturbance in the Sengoku period and requests them for help. Though a bit hesitant, they agree do so after Shinnouske agrees and also by the fact that their schedule will not be affected. The three of them don period-adaptable suits, with Shin chan wearing a special suit that can respond to the unique crisis, and board on an emergency time machine to the Sengoku period.
They land the ruins of the castle in present-day Kasukabe and are attacked by Unkokusai’s henchmen. Suddenly, a mysterious swordsman arrives and fends them off. The swordsman reveals himself to be Fubukimaru, the heir of the castle. Fubukimaru tells them that everything was going well in the kingdom, until Unkokusai arrived. Unkokusai killed Fubukimaru’s lord father and lady mother and captured his sister. Fubukimaru recounts the prophecy, that when castle falls into crisis,”three heroes and one dog” will save it, and believes that the Nohara family are the “three heroes and one dog” and asks them to help him defeat Unkokusai. Though reluctant, they agree to do so, mostly because of the fact that one of Unkokusai’s henchmen stole Misae’s handbag, which contained their bank savings and the legal seal(Hanko) and they wished to reclaim it.
The Nohara family started their journey to Unkokusai’s palace, alongside Fubukimaru and his horse Enji. On their way Misae started to like Fubukimaru, which made Hiroshi jealous. Suddenly, they are attacked by Unkokusai’s henchmen named Matabi. Matabi and Fubukimaru had a fight,though the former was stronger. So, to help Fubukimaru, Shin chan used the “Save3X” feature and was turned into a cockroach, through which he was able help Fubukimaru defeat Matabi. Meanwhile, Hiroshi and Misae came across Unkokusai’s woman sidekick named Ogin, who had Misae’s handbag. Misae asked for it, but Ogin gave her two black balls instead. Misae, then shouted for her handbag. Angry, Ogin turned both Hiroshi and Misae into balls, leaving only Shinnouske and Shiro out of the”three hero’s and one dog “ prophecy.
That night, they stopped at hot spring. Fubukimaru asked Shinnouske to go first. Though he initially refused, Shinnouske decided to go after he learnt that there is young woman inside(because of Shin chan’s habit of flirting with young women), but found that he was tricked, after he found only old people to be inside. After Shinnouske went sleep, Fubukimaru secretly went inside the hot spring to bathe, but unknown to him Shinnouske and Shiro had been following Fubukimaru inside, thus discovering that Fubukimaru is a woman. Fubukimaru tells them that her lord father had no boys as his heir, so he raised her up as a boy. Suddenly, they were attacked by Unkokusai’s henchmen named Tamashiro. Shinnouske uses the “Save3X” feature for the second time and transforms into a frog and helps Fubukimaru defeat Tamashiro. They soon enter in Unkokusai’s castle, where they come across Ogin, who pulls Fubukimaru by her hair. Suddenly, Fubukimaru chops her hair using a dagger and stabs Ogin. Ogin splits out a green smoke on Fubukimaru, due to which her body is unable to move. A paralysed Fubukimaru, gives her sword to Shinnouske and asks him defeat Unkokusai. After getting motivated by Shiro, they both go in search of Unkokusai.
Soon, they enter in a dark room, where they come face-to-face with Unkokusai. Shiro reveals Unkokusai to be the 30th century’s history freak, Pierre Jakoman. Shinnouske and Jakoman have a fight, in which Shinnouske uses his “Save3X” feature for the third time and gets transformed into a samurai. During the fight, Shinnouske’s sword gets stuck at the roof and he transforms into original self and falls. The edge of the sword hits Jakoman on the head due to which he falls from castle cliff. Suddenly, a stranger comes towards Shinnouske wearing an astronaut type suit. The person introduces herself as Ring Strom, an officer from the time patrol in the 30th century. Ring informs Shinnouske , that she only borrowed Shiro’s body and apologises for putting him and his family in trouble. Fubukimaru arrives and meets Ring. Fubukimaru questions Shinnouske about her sister. Suddenly, wind blows from Shinnouske’s body through which his parents and a pretty lady are released. The pretty lady turns out to be Fubukimaru’s sister Yukino. But Fubukimaru reveals that Yukino, is actually a man. From his birth, Yukino believed himself to be a girl, no matter how much his parents tried to convince him. So, to fulfill his lord father’s desire, Fubukimaru became a man
They left the castle and saw the sun rise. Ring thanks everyone for helping her investigate the problem in Sengoku period. As they prepare to leave for their century, Fubukimaru and Yukino bid them a farewell. Afterwards, Fubukimaru is woken up by a soft voice, which turns out to be her lady mother, who asks her to leave for the war (because Jakoman left the century, everything must have become normal). The Nohara family return to their century, but are shocked to find themselves and everyone else dressed in different clothes and that nobody feels it to be weird. The Nohara family watch the TV and are stunned to find out that their new president is Jakmon, who has put a reward to the one who catches the Nohara family. Suddenly, Jakoman’s henchmen arrive, but Ring fends off by wearing a cat suit and explains the Nohara family that they have to defeat Jakoman in order to return to their normal self.
They go to Jakoman’s hideout where he challenges them for fight with his huge robot. Using a Helmet which can make its users imagination come true, Shinnouske builds his own robot(based on his favourite cartoon named Kaantmu robot) to defeat Jakoman. Though at first they are unable to do so, they succeed after Shinnouske uses a technique, which used while playing a game with his mother and defeats Jakoman for once and for all, after which everything becomes normal. The movie ends with Shinnouske’s mother punishing him for embarrassing her in front of his teachers and classmates.