Seira Kandori is a junior high school student at Fūrin Middle School and a member of its baseball club, playing as third baseman. She possesses dark-brown curly hair, brown eyes, and wears glasses. Initially characterized by a heavier physique, her motivation for joining the baseball team stemmed from personal body image concerns and a goal to lose weight for a more slender appearance.

Her early days on the team proved difficult, sparking immediate regret about her decision and fears of becoming a burden to her teammates. This period was marked by anxiety and self-doubt, causing her to question her place within the team. Teammates Daigo Shigeno and Mutsuko Sakura provided crucial support and encouragement, helping her persist through these initial struggles. Their intervention served as a pivotal turning point, allowing her to build confidence and deepen her commitment to baseball.

Driven by a desire not to hinder the team's progress, Seira dedicated consistent effort to practice and improving her skills. This training regimen contributed to measurable development in her baseball abilities. Over time, her initial anxiety diminished, replaced by growing self-assurance both on and off the field. Her journey illustrates a character arc moving from insecurity towards becoming a more determined and reliable teammate, focused on positively contributing to the team dynamic. This path intertwines her personal physical goals with athletic development within the context of team sports.