Maeshiri lives an unremarkable life as an office worker, distinguished by one highly unusual physical trait: his buttocks are located on his front side. Unbeknownst to his colleagues and boss, he secretly leads a double life as the citys masked protector, Oshiri-Mae Man (Butt-Front Man). His routine of balancing mundane work with small-scale heroics is upended when a strange new drug begins circulating through the city, one that causes ordinary peoples posteriors to migrate to the front of their bodies.

Investigating this bizarre phenomenon leads Maeshiri to infiltrate a powerful pharmaceutical company, where he uncovers a conspiracy far greater than a simple narcotics ring. He discovers the Oshiri-Front Empire Revival Plan, a scheme orchestrated by a mysterious and vengeful villain. Ancient records reveal that a once-glorious civilization known as the Oshiri-Front Empire, populated by beings whose buttocks naturally faced forward, was destroyed in a catastrophic conflict with humans who had rear-facing posteriors. Now, this enigmatic antagonist seeks to resurrect the fallen empire and enact revenge on all of humanity.

Recognizing the existential threat posed by this plot, the hero realizes he cannot face this danger alone. He seeks out his former mentor, a seasoned warrior known only as Oshiri-Mae Legend, who was the champion of a previous era. Under the Legends grueling tutelage, Oshiri-Mae Man undergoes intense training to prepare for the coming confrontation. The fate of the world hangs in the balance as he races against time to thwart the empires revival and prevent all of humanity from waking up to find its butt in the front. The film, a work of absurdist comedy from creator and director Takashi Taniguchi, expands upon his series of anime shorts first launched on YouTube in 2018.