Bus Driver

A mysterious, unnamed bus driver who seems to know more than he reveals and constantly shows up to offer advice to Tsukune, he is usually portrayed smoking a cigar. He is the one who requests the board chairman help keep Tsukune's ghoulish nature at bay. It is unknown if the bus driver is human or a yokai, but he does have an extensive knowledge in the supernatural, having identified Ishigami's Lilith Mirror as the cause of the uproar during the school festival. He seems to know about Tsukune secretly being a human being, but it is only subtly implied.

[Spoiler] He is also one of the three Dark Lords

(but this is only in the anime). [/Spoiler]

(Source: Wikipedia)