Izumi Shigeno is the eldest daughter of the renowned baseball player Goro Shigeno and his wife Kaoru, making her the older sister of the series protagonist, Daigo Shigeno. She was born in the United States during her father’s eighth year in the major leagues, following his World Series victory, and she later moved back to Japan with her family after her father retired.

Izumi possesses an energetic and upbeat personality, a trait she shares with her parents. Her passion for baseball was ignited after witnessing her father’s return match for the Oceans, an experience that lifted her spirits after a period of disliking him for being unemployed and inactive following the family’s return to Japan. Initially, she wore her hair in twin-tails during her kindergarten and elementary school years, later switching to pigtails in middle school. Her appearance is also noted for her ahoge, hairclip, school uniform with a ribbon tie, and vest.

Within the story, Izumi serves as a supportive elder sister to Daigo. She worries about him when he becomes lethargic due to his complex about living up to their father’s legendary legacy. She feels relieved when Daigo decides to continue with baseball as a catcher and offers him support based on her own experience in little league. Izumi continues to play baseball and excels in her studies, advancing to Fuurin High School, where she becomes the team’s ace pitcher.

Her notable abilities on the baseball field are significant. She is described as a star when it comes to pitching and is recognized as Fuurin’s ace in the anime adaptation. Her development involves moving from a young girl who disliked her father for his post-retirement behavior to a passionate player who follows in his athletic footsteps, all while balancing her sports commitments with her academic life. She is characterized by her strong sense of responsibility, competitive spirit, passion for baseball, and a dedication to improving her own skills while supporting her teammates.