One night, Shiriri – an alien came to Nohara family, because of Shiriri’s mysterious beam, Hiroshi and Misae turned into 25 year-younger kids.
In order to have Shiriri’s father to change them back into normal again, the Nohara family hides Shiriri into Shinosuke’s bottom and starts their journey across Japan. However, there is a huge conspiracy of Shiriri’s father progressing in their back…