Arahabaki is a great demon who once took control of the body of a Fu-ma ninja. After his host was destroyed, he was sealed within Taki's ninja disciple, Natsu.
The seal placed on Arahabaki weakens each time Natsu taps into her powers.
Arahabaki has been said to be a symbol of rebellion. This could mean that he has an effect on Natsu's personality, for it is said that she is a bit rebellious herself and does not want to "copy" or "look like" her master, Taki.
Natsu's hair makes reference to the body of Arahabaki that has surrounded several snakes to own.
The snake design for Arahabaki may be inspired by Yamata no Orochi (八岐の大蛇, lit. "8-branched giant snake") translated as Eight-Forked Serpent in English, which was a legendary 8-headed and 8-tailed dragon in Japanese mythology who was slain by the storm god Susanoo.
Arahabaki is an ancient Japanese aboriginal god since the Kohun period. The Momunofu were his servants and before his religion was submerged by the Shinto pantheon, Arahabaki was worshiped in Japan's North-Eastern regions. He was also worshiped by Nagasunehiko, an enemy of Emperor Jimmu, and so by the Emperor's orders Arahabaki became a symbol of treachery, rebellion, and heresy and his worship was forbidden for a long period afterwards. Nowadays, Arahabaki's clay figurine is especially common in inns throughout Japan.