Euphemia is the supporting character of light novel, manga, and anime series Instant Death. She's Theodisia's younger sister and a half-demon girl. She was enslaved by Yuuki Tachibana, one of Yoigiri's classmates as one of her bodyguards. She was freed from her brainwashing after Yuuki was killed trying to fight Yoigiri. Later, she happens to meet Lain Tendou, who sucks her blood and turns her into a vampire. After Lain was killed by Yogiri, Euphemia took over all of Lain's abilities and she turned into an Origin Blood Vampire.
Eventually, she meets Risley, a clone of Lain, and Euphemia pledges her allegiance to her as her servant.