Kishukusha No Kuroneko Wa Yoru O Shiranai summary:

The sons of respectable families from all over the world gather at Blanc College High School, a boarding school. Yuki, a first-year from Class A and House X is a scholarship student at the top of his grade. He hangs out with no one and is aloof. The only one who approaches him without apprehension is the head boy, Gene, the object of adoration of the students and someone whose existence is absolute. One day, their classmate, Aura, gets attacked by someone within the school!! On his neck is a bizarre scar which looks just like the bite of a vampire…?!