Saki Ayase is a central character in the anime series 'Gimai Seikatsu'. She is portrayed as a lively and cheerful young girl who becomes the step-sister of the protagonist, Yuta. Having moved into the same household, Saki brings a fresh dynamic to Yuta's life with her vibrant personality and caring nature. Despite the initial awkwardness of their new family situation, Saki quickly becomes an integral part of Yuta's daily life, providing support and companionship. Her role in the series highlights themes of family, understanding, and the bonds that form through shared experiences.