Sapphie is a female Cavalier King Charles Spaniel Jewelpet, one of the three franchise mascots. She possesses lemon yellow fur, cornflower blue ears, and jewel eyes crafted from blue sapphires. She adorns herself with a light pink and light blue flower garland on her head and a white pearl necklace featuring a blue treble clef-shaped sapphire pendant. Some series depict her adding accessories such as a white professor's cloak and glasses. Her jewel charm form appears as a blue, egg-shaped stone embedded with a dark blue star-shaped sapphire encircled by four smaller sapphires. When transformed magically into a human, she retains her tail and sports sky blue hair styled in two ponytails, dressed in a pink vest with blue ribbons and a light blue skirt.

Her personality remains consistently quiet, smart, kind, and empathetic. She exhibits a calm and supportive nature, demonstrating a deep understanding of others' feelings. As the embodiment of friendship, her magic specifically focuses on fostering human connections, enhancing intelligence, promoting calm judgment, and recognizing beauty. She holds the "Crystal Class" ranking, the highest magical level, earned through consistently successful spellcasting. Her incantations include "Puru Puru Prism Jewerhythm! Sapphire Jewel Flash!" for individual spells and group summoning chants performed with Ruby and Garnet. She frequently blends scientific methods with her magic, excelling in invention and experimentation. Tools she utilizes across different series encompass the Mini Jewel Stick, Jewel Pod, Jewel Pad, and Jewel Watch.

Originating in Jewel Land, an accident transformed her into a jewel charm scattered on Earth. In the first series, Aoi Arisugawa discovered her, and Rinko and Ruby awakened her. Sapphie's magic convinced Aoi to remain and search for other Jewelpets, forging a sisterly bond. In Twinkle, she partnered with Sara, a lonely girl, acting as her lab assistant and encouraging her emotional openness. During Sunshine, she attended Sunshine Academy as a student and biologist, managing a secret lab where she created a robot named Nejikawa, who developed feelings for her. Her ambition includes becoming an astronaut, though a temporary dark magic possession amplified selfish tendencies.

In KiraDeco, she resided in a cluttered library-home and partnered with Kiichi Furano of the KiraDeco 5. She lectured at a school lacking teachers and sought a Philosopher's Stone to decorate her Jewel Pod. Her personal habits reveal a contrast between intellectual brilliance and domestic untidiness, leading her to rely on Kiichi for household management. For Happiness, she worked at the Jewelpet Café Happiness alongside her partner Nene Konoe. She aided Nene in revitalizing her family's department store, resulting in their first Magic Gem formation. She later generated a secondary Magic Gem with Azusa-sensei.

In Lady Jewelpet, she mentored Charon, guiding her transformation into a refined lady. During the OVA Attack Chance, she invented a microwave for a cooking show, though it malfunctioned due to Ruby's interference. She appeared in the movie Sweets Dance Princess as one of the first Jewelpets entering Sweetsland for Princess Mana's birthday. Her development across media involves shifts in focus—from a supportive partner in earlier series to a science-driven student in Sunshine, and later, a community-oriented figure in Happiness. Instances of brainwashing by antagonists like M-Kage and the Red Moon temporarily altered her behavior, but she consistently returned to her core traits of loyalty and intellect.