Momoe Uesugi is a teenage girl and a central character in the series. She is portrayed with short brown hair and a tomboyish appearance, frequently seen wearing a baseball cap and carrying a bat. Her background is shaped by her father's role as a baseball coach, which instilled in her a deep love for the sport. She is a skilled baseball player and actively helps her school's baseball team. It is through her involvement with the team that she meets the protagonist, Teppei Uesugi.

Her personality is marked by a no-nonsense attitude and a strong will, yet underneath she has a kind heart and is deeply loyal to those she cares about. She and Teppei initially clash due to their contrasting temperaments, but over time they form a close bond and develop romantic feelings. Momoe becomes Teppei's most steadfast supporter, cheering him on during his matches and standing by him through challenges. Her presence serves as a grounding force, reminding him of the importance of family and support. While she is a secondary figure in the overall story, her dedication, willingness to put others before herself, and unwavering loyalty make her an important emotional anchor. Her notable abilities lie in her athletic talent, particularly in baseball, and her calm determination.