18+ Crayon Shin-chan Gaiden: Kazokuzure Ookami

Master butt-swordsman Hiroshinosuke Nohara (Lone Wolf) travels with his family seeking employment. The family encounters a mysterious girl Hazumi and a wild dog Shiro, and decides to travel together. The group is attacked by various assassins, eventually their lives are threatened by the butt-swordsmen's enemy, the armpit-swordsmen of the Demon Bull Clan. Who will win: butts or armpits? Against an array of idiosyncratic enemies, Hiroshinosuke Nohara and his son Shinnosuke have the chance to display their swashbuckling skills.

(Source: ANN)