Kōmori Nazo (謎こうもり Nazo Kōmori) better known as Kou, or Kō-chan (Ko-buddy and Batty in English to Kokoa) 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 Gin and the succubus Kurumu Kurono) into loving and obeying him. He was stopped by Inner Moka and Kokoa. 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!").
Most of the time, Kou looks like a cute bat with a hamster-like body, but he can shapeshift into various weapons at Kokoa Shuzen's command. In the anime, he once took the form of a tall boy with dark blue hair. His chibi form is a bat, while his real form is a star-like creature with teeth on the upper side of each point.
In the anime, he is shown to be loyal to Kokoa most of the time, but was disloyal for a time when he wanted to use his allure powers in human form to make the female students at the school fall for him, planning to enslave Kokoa as well, but was defeated. He is also stated to eat a lot by Kokoa.
Kou appears as Kokoa's bat, though he is named "Batty" by Kokoa. Like his anime counterpart he can change into a variety of weapons. It is revealed in Moka's memories that Kou was originally caught by Kokoa as a gift for Moka, but she passed and gave it back to Kokoa instead.
The main reason being is that the bat weighed 100kg and Moka said it was too heavy. Naturally Kokoa is capable of carrying very heavy weapons, plus Kokoa was durable to begin with.
Kou appears as censoring of fanservice and is the narrator. He likes to state the exact duration of a fight.
Kou is shown to be Kokoa's servant. He is also revealed as having the ability to be a Transformer Bat, capable of becoming a variety of weapons for Kokoa's use. In episode 10, he tries to betray her by taking the form of a tall bishōnen and using his allure powers to make the girls at the school fall in love with him and serve him, planning to make Kokoa his loving slave too, but he fails, and returns to being her servant at the end of the episode.
- Shapeshifting: Kou has the ability to shapeshift into weapons in the manga. It's also noted by Kokoa in an omake that his "Cute" bat form, is not his actual form, and remarks that she's never seen his true shape (though at the same time she said this, he assumed a monsterous form to eat a nearby insect, terrifying Moka and Tsukune while still rendering Kokoa ignorant to the event.) It is also worth noting that his power allows him to change form, but not mass, meaning he will always weigh the same in any form he chooses to take - this makes him a useful weapon. In the anime, Kou has shown to shape shift into human form but only once.
- Weapon Forms List: He has been seen asumed several forms such as:
- Spiked bat
- Nailed bat
- Bone saw
- Morning star