Kaien Cross is a character from Vampire Knight
The headmaster of Cross Academy (the main setting o the series) and current head of the Vampire Hunters Association, he is a very powerful vampire hunter (which is both a profession and a race of genetically superior humans). Even for a vampire hunter, the amount of vampire genes on his body is abnormally high, rendering him superior to most vampires.
It is hinted that he might have eaten his twin on his mother's womb (a general fact on powerful vampire hunters) and his strength, speed and reflexes rendered him the title of "vampire without fangs" (or "fangless one"), as he was able to surpass the abilities of any human being by far.
Powers and abilities
Kaien ages extremely slowly, and looks like he's in his mid 20's even though he is currently over 200 years old. He is a very strong vampire hunter, known as the best of them until his retirement. Kaien also emanates an aura that resembles that of a vampire, which causes other hunters to mistake him for an undead in several occasions. Kaien is considered a legend among vampire hunters.