Ruby Hoshino「星ほし野の瑠る美び衣い, Hoshino Rubii?」, more commonly referred to as just Ruby「ルビー, Rubī?」, is the female protagonist and one of the titular characters of Oshi no Ko. In her previous life, she was known as Sarina Tendouji, a terminally ill patient who was cared for by Gorou Amamiya and, following her death, was reincarnated as the child of her favorite idol, Ai Hoshino.