Himura Kaguya is a character from the side story; Shinku ni tokeyuku omoi no hate ni. He is the leader of a clan of vampire-species Duras who left Infernus over 300 years ago.
His real name is Crime Caesar and was an S-ranked Duras. He was considerably famous in Infernus. He later fell in love with a human woman named Sara and becomes good friends with Yuki.
He is a Duras who oddly loves humans, which he says himself numerous times, wishing he could be one himself. He dies in Yuki's arms saying, "If I die for humans, that is all I can wish for and I can pay for my deeds…"