Exhausted from days of her husband's continued absence, Ririka reluctantly joins "Chukou GP," an anal review panel attended by anal enthusiasts. Thrown into a dark, sealed basement, she begins a grueling regimen of bodily training to win the title of Best Anal. At the event, every aspect of her anus is scrutinized—the color, shine, number of wrinkles, and even the deepest interior. Enduring immense humiliation, her tormented anus betrays her will, climaxing repeatedly under relentless stimulation. Amid this ordeal, she searches for the true answer to what she must become.