Among Ayakashi, those classified as humanoid (not to be confused with those who merely have some human features) are considered to be the most dangerous, both because of their superior intellect and their tendency to operate in groups. There is also a theory that their underlying desire, whether they recognize it or not, is to become human.
There have only been two confirmed cases of humans becoming Ayakashi. In each, a man with a strong desire for greater power made a conscious choice to discard his humanity and embrace a new life as an Ayakashi.
- Kaguro: Kaguro described his human self as a powerless outcast that chose to abandon the world and obtain total freedom as an ayakashi In the anime, he was a swordsman in search of more strength, and began to challenge and kill famous swordsmen in his quest. He met a Kekkaishi who tried to destroy him (recognizing that he was on the path to becoming a demon), but fled in fear after witnessing his Zekkai. Kaguro encountered three Ayakashi that invited him to cross over into their world. After defeating his only friend in a battle to the death, Kaguro became an Ayakashi and was able to enter their world.
The leading Ayakashi of Kokuboro all have human forms that they spend most of their time in, and even have a standing rule that they only speak to each other while in those forms. Hakubi states that given enough time, some Ayakashi can assume human form, but most do not because it is too much trouble. However, the reverse seems to be true in Kokuboro: their human forms conserve power, and are generally considered more appealing or more suitable for formal meetings. Assuming their natural, most powerful state is saved for important battles, and doing so any other time is usually due to a lack of self-control. Kokuboro also manufactures human skin disguises, which protects them from sunlight, and also conceals their yōki, rendering them undetectable to Kekkaishi.
- Princess: Her true form is a nine-tailed kitsune, but even in her human form, her nine tails remain.
- Gagin: His true form is a six-armed centaur.
- Aihi: Her true form is large flower with countless vines.
- Shion: Her true form is never revealed.
- Koshu: His true form is a small octopus.
- Hekian: His true form is never revealed.
- Sakon: His true form is a humanoid armored lizard.