Sophie is an 8th grader at Paprika Academy.
She has been working in the idol industry since she was very young. Admired by other students she has her own fanclub and appears in TV frequently as soloist.
When Sophie eats a so-called Red Flash (pickled plum), her personality - likewise with her appearance - changes to be an confident and impressive idol.
On the contrary she is the complete opposite in everyday life - extremely soft-spoken, disoriented and sluggish. It is also hinted that she has low blood pressure. Her hair becomes messy and covers her eyes and is mostly shown wearing a grey sweat suit.
Even her friend Lala couldn't recognize her for the first time due to her drastic shifting.

Since she began forming her friendship with Laala and Mirei, she has been working to take more care of herself but also shows more of her true self in public.
Despite the fact that Sophie is often absent-minded, she happens to be very perceptive and can pick up on tiny details others would normally miss.

(Source: PriPara Wikia)