Erionelle

Erionelle (エリオネル Erioneru) is new transfer student to Setsuna's class. Little is known about her, except that she is the princess of Adenbulk, the Western Oni World. With soulless eyes and long black hair that goes down to her legs, she has been tasked with the assassination of the two demon princesses under the orders of her father. Unlike the other Oni shown so far, she shows absolutely no desire to obtain the Banriko Heart and only wishes to eliminate the White and Black Princess Kanna and Rena, so she wishes to destroy the Banriko Heart.

Afer being defeated and humiliated by Kanna she want Kanna to kill her but being stopped by Setsuna, since that time she fall in love with Setsuna

She appear again in 2 last chapter, she want to take Setsuna and life with him in her homeland and also she come to neutralize the Banriko inside Setsuna and give him a new body so he can continue to life as a normal human

In last chapter she come with bride dress to Setsuna home and take him away so they can life together in her homeland but they being chased by Rena, Kanna and also Arima