Sophie Senoo, originally named Aiko Senoo, transfers into Doremi Harukaze's class and joins the main group. Hailing from Osaka where her family runs a takoyaki shop, she exhibits a practical and hardworking nature. She initially speaks with a Kansai dialect, though this detail varies in localization.

Sophie discovers Doremi and Hazuki Fujiwara's secret by accident, leading her into their magical world and responsibilities as a witch apprentice. Her personality blends confidence, athleticism, and occasional bluntness, making her the group's pragmatic voice. Her competitiveness shines in sports, alongside moments of vulnerability like fearing she might fail her team as the anchor in a swim relay.

Throughout the series, Sophie helps raise Hana, the future Witch Queen, and manages the transforming Maho-Do shop, which becomes a gardening store and later a bakery. She navigates personal challenges, including reconnecting with a childhood friend, Anrima, who once made a marriage promise to her.

In the OVA *Ojamajo Doremi Na-i-sho*, set during *Mo~tto! Ojamajo Doremi*, Sophie confronts her swim meet insecurities with determination. Another OVA episode delves into her past through Anrima's reappearance.

Her straightforward personality influences her magical abilities, often using spells for practical solutions. In the final season, *Ojamajo Doremi Dokkān!*, Sophie and her friends face a pivotal choice: become full witches or return to normal lives. They choose to relinquish their magic to stay with their families and pursue human dreams, cementing their bond and growth.