Sekia

Sekia is one the ayakashi chosen to accompany Kaguro's advance guard during their daytime invasion of Karasumori. Sekia is an outgoing, fun-loving ayakashi with a childlike, raspy voice. When he was able to enter the human world during the day for the first time, he seemed very intrigued with many of the human necessities and attachments, wanting first dibs on it all. He is more of a follower than a leader, which fits his personality quite well. Sekia may be the villian but out of his group, he is the most good-natured and concerned one out of them. His ayakashi form looks like that of an octopus.

(Source: Kekkaishi Wikia)