In the context of the anime Aim for the Ace!, the character referred to as Jenny is the protagonist, whose original Japanese name is Hiromi Oka. The name Jenny was adopted for her character in several European localizations of the series, most notably the Italian version where she is known as Jenny Nolan.

Jenny is introduced as a 14-year-old freshman in high school. At the outset, her decision to join the school's prestigious tennis club is not driven by a deep passion for the sport itself but by more personal and romantic reasons. She is secretly in love with an older student, Takayuki Todo, and joining the club is a way to be near him. She also greatly admires the team's star player, Reika Ryuzaki, a graceful and nationally famous player known as "Madame Butterfly," and hopes to emulate her.

Personality-wise, Jenny is initially portrayed as impulsive and somewhat childish. She is full of the typical dreams and hopes of a girl her age but lacks confidence in her own abilities. Her mental weakness and tendency toward anxiety are central aspects of her character, as she often loses faith in her tennis skills when faced with pressure or setbacks. Despite these insecurities, she possesses a core of resilience. Her enthusiasm for tennis grows over time, and even after facing crushing defeats, sacrifices, and emotional turmoil, her spirit does not break. Her love for the sport and her refusal to give up become her greatest strengths, pushing her to continue striving for excellence.

Her role in the story is that of the determined underdog. The new and demanding tennis coach, Jin Munakata, sees great potential within her. He becomes the most significant figure in her life, putting her through a long and grueling series of training sessions to mold her into a champion. This rigorous training is often harsh, forcing Jenny to confront her weaknesses head-on. A key part of her journey involves a romantic conflict; she falls in love with Takayuki Todo, but Coach Munakata advises her to put aside these feelings, warning that getting too involved will distract her from her goal of becoming a top player. This internal struggle between her heart and her ambition is a recurring challenge she must overcome.

Jenny's key relationships are central to her development. Her bond with Coach Munakata is complex; he is an inflexible and stern taskmaster, yet he is deeply devoted to her success. Her friendship with Maki Aikawa provides her with consistent and sisterly support, acting as a confidante without any jealousy over Jenny's growth. Her relationship with her idol, Reika Ryuzaki, evolves over time. While Reika initially becomes jealous of the attention Munakata gives to the newcomer, the two eventually learn to become friends and rivals who push each other. Similarly, her relationship with Takayuki Todo transforms; as her dedication to tennis deepens, her initial crush fades, and he becomes a good friend and supporter.

Throughout the series, Jenny undergoes significant development. By persevering through immense physical and emotional trials, she slowly transforms from an anxious, love-struck girl into a mentally strong and confident athlete. The support of her coach and friends helps her channel her passion for tennis into the discipline required to become one of the best players in the world. Her notable abilities lie not in innate, flashy talent, but in her powerful will to improve. Coach Munakata identifies her as a raw gem with clear potential, and through her relentless hard work, she develops the skills necessary to compete at the highest levels of the sport.