Black Sister is a fictional character from Choujigen Game Neptune, also known as Hyperdimension Neptunia. She is the younger twin sister of White Sister and the human form of the CPU candidate Noire. In the series, she appears as a lively, sharp-tongued, and competitive girl who often gets into arguments, especially with her sister. She serves as a supporting character and a younger counterpart to Noire, contributing comic relief, sibling rivalry, and additional insight into the world of the CPU candidates.