Based on the real-life racehorse nicknamed "The Gray Monster," Oguri Cap is a horse girl born with a weak knee. Her mother dedicated daily massages to strengthen it, transforming this weakness into the foundation for her running ability. Her early life involved financial hardship, implied to stem partially from her substantial appetite. Her mother's encouragement instilled a deep love for racing and a dream to become the fastest horse girl. She began her career at Kasamatsu Tracen Academy, a regional institution focused on local competitions. Academically unprepared and socially naive, she maintained a country-girl innocence, often oblivious to social dynamics like bullying from peers such as Norn Ace, Rudy Lemono, and Mini the Lady. She possessed an extraordinary capacity for hard training and a voracious appetite that became legendary among cafeteria staff. Despite enduring sabotage attempts before races—including untied shoelaces—her raw talent and unique, powerful running gait allowed her to dominate opponents. Her coach, Kitahara Jou, recognized her potential as a transformative figure for the struggling local racing scene, calling her "someone you can root for from the bottom of your heart." Early rivalries shaped her journey: Fujimasa March viewed her as an "Always Someone Better," though Oguri Cap initially remained unaware of this competitive tension. Norn Ace shifted from antagonism to obsessive fandom after a decisive defeat. Advancing to central competitions, bureaucratic barriers initially barred Oguri Cap from elite races like the Japanese Derby due to technicalities. A petition by reporter Sensuke Fujii and advocacy from Symboli Rudolf—who related to Oguri's disqualification circumstances—eventually secured her entry. Her victory there, by a seven-length margin, earned her the title "The Cinderella of Kasamatsu," symbolizing her role in carrying regional hopes. Following this triumph, a period of demotivation arose when she was excluded from certain prestigious races. Witnessing Tamamo Cross's victory and a pivotal phone call with the also-struggling Fujimasa March reignited her determination. March's metaphor about "moving to the next mountain" resonated, reinforcing Oguri Cap's resilience. Her story continues as she ascends toward national stardom, embodying perseverance amid competitive and personal challenges.