Olivia is a Japanese-born student with foreign parents, possessing blonde hair and blue eyes that mark her as looking foreign. Despite this appearance, she struggles with English, contrary to expectations based on her heritage. Her Japanese is native-level, having been born and raised in Japan, but she deliberately affects broken Japanese to maintain a false identity as an American transfer student. She pretends not to understand Japanese fluently. This deception becomes challenging when classmates like Kasumi seek English lessons from her.

Her background includes attending an all-girls middle school. There, her language ruse is challenged by a teacher who notes her excellent Japanese test results versus her poor English performance. Confronted, Olivia panics but refuses to speak normally, continuing the charade despite the risk. This leads to recurring comedic situations where she fabricates English phrases—like falsely claiming "give me chocolate" is a common American expression—to hide her lack of knowledge.

Olivia exhibits a generally carefree and occasionally oblivious demeanor, though she becomes anxious when her fabricated identity is threatened. She manipulates situations to evade accountability, such as deflecting English lessons by feigning interest in Japanese pastimes. Her relationships with classmates Hanako and Kasumi involve reciprocal manipulation and escalating slapstick conflicts, often culminating in physical humor like slapping games. These interactions result in the formation of the Pastimers Club, where the trio engages in various activities.

Distinctive traits include a noted lack of concern for personal hygiene, resulting in body odor mentioned by peers. She also displays moments of impulsivity, such as cutting her own hair out of boredom, leading to comedic outcomes. Physically, her blonde hair and blue eyes contrast with her clubmates, traits occasionally highlighted in jokes about her foreign appearance versus her actual Japanese upbringing.

Within the Pastimers Club, her dynamic blends camaraderie and self-serving behavior. She leverages Kasumi's desire for English lessons to negotiate exchanges for Japanese pastimes, though her incompetence in English strains these arrangements. Her interactions with Hanako fluctuate between collaboration and petty rivalry, often centered on Hanako's envy of others' traits or status.

No significant development occurs regarding her core deception; she maintains the pretense of being foreign despite mounting complications. Her role remains consistent as a source of linguistic farce and physical comedy, with no indication of abandoning her fabricated identity or improving her English skills.