Riru Orito is a petite second-year student at St. Francesca Academy, standing 146 cm tall and weighing 40 kg. She sports mint-green hair in long twin tails with blunt bangs and has brown eyes. As a classmate of protagonist Akihito Hayasaka, she exhibits an energetic, cheerful, and strong-willed personality, though her mood fluctuates between kindness and coldness. This temperament sparks frequent minor quarrels with Akihito, yet they maintain an underlying friendship. She deliberately provokes him and makes disparaging remarks.

Riru belongs to the swimming club, wearing a sports swimsuit during activities. She harbors deep admiration—and initial romantic feelings—for swim club captain Reika Matsubara. These feelings remain unreciprocated due to Reika's existing lesbian relationship with fellow swim club member Yūki Arise. After detecting inconsistencies in Reika’s behavior, Riru enlists Akihito to observe her.

Her family’s financial hardship drives diligent development of domestic skills like cooking and candy making, a work ethic extending to academics and club activities. Riru enjoys discussing her attraction to cute girls, often triggering arguments with Akihito.

Across official media, Riru undergoes significant development regarding her romantic feelings. Following a pivotal encounter with Akihito, she relinquishes her unrequited attachment to Reika. This transition features prominently in the second volume of the OVA adaptation, where she commissions Akihito to observe Reika due to relationship doubts. Their interaction culminates in her emotional resolution.