Olivia Yūki is one of the main characters of Onegai AiPri. She is a second-year middle school student at Onegai Middle School and serves as the student council president, placing her one school year above the younger protagonists of the story. She has round lime green eyes with yellow flecks and long, wavy orange hair worn in a half-ponytail at the back. Her birthday is March 22.

Olivia originally comes from outside Onegai Town. Her family includes an older brother named Aran and a younger brother named Leon, with her parents also part of her household. As student council president, she presents a composed and responsible front, but her true nature is quiet, shy, and inclined to overthink. She has difficulty turning down requests and tends to find courage not for her own benefit but for the sake of others, which reveals a gentle and selfless character.

Her most defining trait is her love of AiPri. She is secretly a devoted fan with extensive knowledge of the idol princess world, and when the subject comes up she becomes so enthusiastic and talkative that she worries about standing out from those around her. This led her to hide her interest and even pretend to dislike AiPri, as she struggled with her own inability to stay quiet about it. That changed when a live performance by the idol Gumi reached her heart and helped her open up. Olivia was then reborn as the idol princess who governs courage and became the fourth member of the group called the Onegai Kanae-tai. In her role as an idol princess, she performs live shows and is capable of achieving a Buzzlium Change, the mark of a fully fledged idol princess. Her personal development centers on moving from concealing her passion out of shyness to embracing it openly, while her relationships with Gumi, Inori, and Aoi deepen as she works alongside them to help fulfill people's wishes.