Maris Stella curates the Tokyo Art Museum's Ueno location. She first met Reiji during the "Girl of the Shell" investigation. Her typical communication is minimal, expressed through fragmented Japanese sentences, yet she shifts dramatically to fluency and detail when discussing paintings or art. She possesses very long, straight blond hair, parted to the side and reaching her waist or beyond, pale skin, blue eyes, and a mole somewhere on her body. Her slim build matches her young adult appearance. She often wears a dress accessorized with a beret, gloves, and a string ribbon tie.

She exudes mystery and strikes others as strange, frequently appearing absentminded or lost in thought. Interactions find her generally taciturn. Professionally, she engages in drawing and painting. Orphaned in her youth, she shares a significant past connection with the serial killer Shinji Mamiya, dating back to a close childhood relationship. She organized an art exhibition featuring Shinji Mamiya's works centered on rebirth, guiding visitors and providing detailed explanations, including for pieces sourced from private collections, indicating a maintained connection. During this exhibition, she intervened to stop Reiji from smoking while simultaneously sharing her knowledge about the displayed artworks.