Souju Shirogane is one of the twin sisters in the anime series 'Futakoi.' She is known for her calm, gentle, and elegant demeanor, often acting as a balancing presence to her more energetic twin, Sara. Souju is deeply devoted to the protagonist, Nozomu, and plays a significant role in the series as a romantic interest. Her refined personality and emotional maturity make her a beloved character, contributing to the central themes of love and companionship throughout the story.