Sier is Dier's older sister, and considering his poor accounting skills he mused about making a Doll replica of her, since his sister was occupied with her own business. Sier later worked as Dier's accountant while also doing the tasks Dier shouldn't, such as handling female Dolls clothing. Sier care about and sometimes impart tough love on her younger brother, but when asked about their radically different hair color, Sier hints that there is more to the sibling's past than it appears.