In a world where racehorses speak, form friendships, nurse grudges, and stage dramatic love stories, Umanari 1-Furlong Gekijō unfolds as a long-running comedic anthology based on real events in Japanese horse racing. The series began in 1989 under the title Sore Ike Okabe Kun before being renamed the following year, and it continued for three decades until 2019, spanning over one thousand installments across multiple publications. The setting shifts between the racecourse, the stable, and even the afterlife, where deceased horses and trainers appear with halos, floating on clouds while still interfering in the affairs of the living.

The manga employs a star system in which well-known horses from racing history return as recurring characters, though their personalities and roles may change from episode to episode, as the author has described them as actors playing different parts in each story. Sunday Silence appears as a fiercely proud stallion with a bulging anger vein on his forehead who refers to himself with a noble title and descends from the heavens to bite his own offspring when they lose important races. Oguri Cap, the self-aware idol horse, makes dramatic entrances in a spotlight with fanfare music, adores attention, and shares a long-standing mutual dislike with Sunday Silence. Symboli Rudolf, the Emperor, dresses in aristocratic Western clothing, travels by horse-drawn carriage even though he is himself a horse, and maintains a complicated, tsundere relationship with his former jockey.

Other notable cast members include Turf Devil, an original character in a black demon costume who tries and largely fails to prevent record-breaking performances, as well as Rice Shower, who carries a metal club specifically to smash the winning streaks of champion horses. The manga also features romantic storylines, such as the tale of Daitaku Helios and Daiichi Ruby, two mile-specialist horses whose pride prevents them from confessing their feelings until after death.

Notable narrative arcs develop organically from real racing rivalries and coincidences. The Broccoli Club series follows a group of talented but consistently unlucky horses who never quite win the biggest prizes, with Stay Gold serving as a scout who recruits new members to this bittersweet fraternity. The Trading Company series reimagines major stallions as corporate executives negotiating business deals. A recurring meta-humorous thread involves the author herself appearing in the manga to complain about purchasing expensive screentones only to have a blue-coated horse retire early or to joke that a gray horse simply had her tones forgotten. Through four-panel episodes that blend slapstick comedy with genuine pathos, the manga chronicles thirty years of racing history while maintaining the central conceit that every race tells a story, and every horse has a voice.