Mutsuki

Mutsuki is a dark stalker, long ago mistaken for vampires. While dark stalkers don't drink blood, they prefer night to day and can levitate high in the air for long periods of time.

Mutuski is the Black Rose knight, the position his older brother was supposed to take, but because of a series of tragic events that lead to him killing his brother, Mustuki became not only the Black Rose knight but the last dark stalker as well. After words, Mutsuki was so upset with himself he sealed himself in a coffin where he was discovered present day by Tenjou who took him in and let him sleep in the basement.

Those two are as different as water and fire, so they refuse to look at each other as friends.