|Occupation(s):||Zoldyck Family's butler|
Kasuga was a female butler of the Zoldyck Family who had the duty of taking care of Alluka after a butler with the same duty, Yasuha, had wished to be made a billionaire. Illumi told her that if she listened to Alluka's requests he would overlook her forbidden romantic relationship with a man she met on the Internet. Shortly afterwards, Alluka asked her to give him 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, resulting in her, her lover and 65 other people, including her teachers and classmates inside the Zoldyck estate, being crushed to death at the same time.