Kasuga

Kasuga (カスガ, Kasuga) is a female servant of the Zoldyck family who had the duty of taking care of Alluka Zoldyck after the previous servant Yasuha had wished to be made a billionaire.

Background
Illumi made a deal with her that if she listened to Alluka's requests he would overlook her forbidden romantic relationship with a man she met on the Internet. When she was with Alluka, he asked for her liver, duodenum, spine and brain continuously, which were all declined by Kasuga. As a result, the cost of the billionaire wish made previously by Yasuha was transferred to her and she, her lover and 65 other people, including her teachers and classmates inside the Zoldyck's estate, were crushed to death at the same time.