Kōmori Nazo (謎こうもり Nazo Kōmori) better known as Kou, or Kō-chan (Ko-buddy and Batty in English to Kokoa Shuzen) is a Transformer Bat acting as the narrator for the animated adaptation. Occasionally covering up various shots of fanservice (done in the television broadcast, while the DVD version is uncensored), Nazo also enjoys stating the exact duration of a fight. In the manga, various bats of similar design are used to give information on the various monsters encountered at the academy. He is Kokoa's bat, but he is named "Batty" or "Kou-Batty". In the anime, he is still Kokoa's bat in season 2. He once went to the school and pretended to be a transfer student and named himself Kōtarō Ijūin, charming almost everyone (including the male werewolf Ginei Moriokaand the succubus Kurumu Kurono) into loving and obeying him. He was stopped by Inner Moka and Kokoa Shuzen. Also, in the anime, it can be thought that he wants to marry Kokoa, as in episode 10, when he thought about enslaving her, he pictured her in a wedding dress, with her hair all down and looking happy, saying: "I love you, Kō" (大好きこ, Diasuki Kō) ("I love you, Kou") (lit. also "I love you Ko!”).

Voice Reference: https://www.youtube.com/watch?v=EVN6yu16Ra4 3:43