Yuki is the Queen of the Fangires from the World of Kiva. Her true form is the Thorn Fangire, whose true name is Perishing at the Altar, Silence from a Deep Kiss.
She is a sea cucumber Fangire that belongs to the Aqua Class Tribe and able to execute her own version of the "Final Zanvat Slash". Though she supports Wataru, Yuki actually sides with Apollo Geist, marrying him to give him immortality so she can have a place in Dai-Shocker. When Tsukasa crashes the wedding, the Thorn Fangire fights him and is killed by Decade Complete Form with Ryuki Survive's power.