Mayuri Shiina, often called Mayushii by her friends, is a central character in the Steins;Gate universe and appears in the film Steins;Gate: The Movie - Load Region of Déjà Vu as a member of the Future Gadget Laboratory. She is the childhood friend of Rintaro Okabe and one of the earliest members of the lab, known for her gentle and innocent demeanor. In the film, she continues to embody the emotional heart of the group, providing warmth and stability in the peaceful Steins Gate worldline that Okabe fought to achieve. Her personality is characterized by a childlike optimism, a soft-spoken manner, and a heightened sensitivity to the moods of those around her. She dislikes conflict and strives to maintain harmony, often acting as a calming influence when tensions rise. Her signature greeting is a cheerful "Tuturu," and she has a habit of reaching her hand toward the sky in a gesture Okabe dubbed the "Stardust Shakehand." Mayuri's primary motivation is to preserve the happiness and togetherness of the laboratory members. She holds no grand ambitions for time travel or scientific discovery; instead, her focus is on the everyday joys of friendship and simple activities. When Okabe begins to vanish from reality due to an overload of his Reading Steiner ability, Mayuri, like everyone else, initially loses all conscious memory of him. However, she retains a vague, unexplainable sense of loss, which manifests as a lingering melancholy. Her role in the story is that of an emotional anchor. Despite her lack of scientific expertise, her subconscious connection to Okabe becomes crucial. When Kurisu Makise, the film's protagonist, searches for a way to save Okabe, Mayuri's faint feelings of déjà vu and her desire to keep the lab open serve as catalysts that encourage Kurisu to persist. Mayuri's key relationships are with Rintaro Okabe, whom she has known since childhood and whose inner struggles she can often sense, and with Kurisu Makise, whom she supports with unwavering kindness during the crisis. She also shares close bonds with the other lab members, acting as a sister figure who diffuses stress and fosters a sense of belonging. Throughout the film, Mayuri does not undergo a dramatic personal transformation; rather, her steady presence and innate empathy are highlighted. Her notable abilities are not supernatural or technical but lie in her emotional intelligence and her capacity to create a safe, comforting environment. She functions as the group's moral compass and a reminder of the ordinary life worth protecting, making her an indispensable part of the story even when her direct actions are limited.