The angel of the demon (Okumura-sensei's love story)

Yukio x oc Yui was Yukio's childhood friend and became his partner for one year. Yui and Yukio became Shiro and Shura's Students; they become close to each other and have feelings with each other. 2 years ago when they were having a mission, Yui was slashed by a demon and lost all of her blood so Yukio gave his blood. ( available in wattpad or FanFiction ) -Jme-