You are Yuu's younger Sister...And Yuu kills Vampire Because His Lover Mika Was thought to be killed by One...

one Day They Saw eachother again But Yuu Wasn't looking Like a Human Anymore something Black came from his back and Yuu had one eye completly Blake and one Red he was Attacking Everything...Mika only wanted to save Yuu*

Mika: "Y-Yuu?..."

you and Mika froze as you both stared at Yuu