Julia MacKenzie is a student at Hokuei University and an active member of the university's volleyball team. Originally from the United States, she has a notable athletic background that precedes her time in the anime's setting. During her high school years in the US, she established herself as the best basketball player in the country. Despite this achievement in basketball, her true passion lies elsewhere. When asked why she did not join a basketball team at the university, she stated her preference clearly, explaining that while she likes basketball, she loves volleyball.

In terms of personality, Julia is characterized by a relaxed and easygoing nature. She operates at her own pace and is not the type of person who becomes stressed or bothered by minor issues. This carefree attitude extends to her social interactions and activities, as she is known to join games and participate in events even when she does not fully understand the rules, approaching these situations as if it were the most normal thing in the world. Her physical description notes that she is a big individual, which is a defining aspect of her character design within the context of the series. A specific, recurring detail about her character is a tendency to forget to shave her underarms, further emphasizing her unbothered and unfussy personality.

Julia's role in the story is primarily as a club member at Hokuei University, where she brings her athletic prowess and unique personality to the group dynamic. Her motivations are rooted in pursuing her genuine love for volleyball, a sport she prioritizes over basketball despite her exceptional talent in the latter. Her background as a former star athlete in a different sport adds depth to her character, illustrating a journey of choosing personal passion over past success. While specific details regarding her key relationships, character development arc, or a full list of notable abilities beyond her athletic achievements are not extensively documented, her identity is firmly established as a confident, large-statured American student who follows her own path and values enjoying her chosen sport above all else.