Takao Hiyama is a teacher in Yuki's school and is the serial killer reported within its vicinity. Not much is known about Takao character-wise, since the man was only given four lines of dialogue in the series, all related with finding and being surprised by Yukiteru. He is the Third diary owner. His "Killer" diary records the location of his next intended victim. It is a handy diary if one knew the true identity of the other diary holders and wishes to take the offensive in the game, but it does little in the way of anything else.

Takao wears a heavy trenchcoat complete with a hat and mask that hides his identity when stalking prey, and carries a large machete as his weapon of choice.

He is named after Vulcan — roman god of blacksmithing.