Yuri Oshimoto is a 15-year-old first-year student at Kameido High School and a member of the tennis club, standing 162 cm tall and weighing 53 kg. Within the club, she uniquely possesses genuine tennis skills and exhibits a serious dedication to activities. This contrasts sharply with her teammates' eccentric behaviors, firmly establishing her as the group's primary straight man. She routinely reacts with surprise or exasperation to their unconventional actions and ideas.

Her family includes a younger brother, Yota Oshimoto, a middle school student. Yota occasionally interacts with the club members, notably Nasuno Takamiya, who employed him as a butler at her family's vacation cottage during summer break, where he performed tasks under her direction. Yuri's connection to these events stems from her brother's involvement.

The tennis club rarely engages in conventional tennis practice or matches. Instead, Yuri endures random and absurd adventures instigated by her teammates, such as encountering aliens, assisting a cake shop with financial troubles, visiting an army base, and going skiing. Amidst these situations, she consistently serves as the voice of reason, attempting to navigate or mitigate the chaos caused by the others' unpredictable actions and misconceptions. Her presence provides a grounding counterpoint to the surrounding surreal comedy.

Across the series, its seasons, OVAs, and related spin-offs, Yuri exhibits no significant character development or alteration to her core traits. She remains steadfast as the responsible and relatively normal member, reacting to the persistent absurdity. Details about her background beyond her immediate family relationships and school club involvement remain unexplored.