Kanna

"Myself and Kanna... are actually one being. When Sōkudo returned my stolen powers, it was best to seal away that power until the need for that power had arrived. Kanna is the fragment of my being of which the true nature of Shinbyeong lies within. When we once again become one, our power is released. My true power... as Kawahiru Madara."

- Kamui speaking of Kanna and himself.

Kanna (神無, Kān'na) is a mysterious young girl that appears to be a member of the Tenka Clan. Apart from being a Sōzōshin, she herself is a sealed part of Kamui's strongest powers, thus existing as the container of which holds the latter's true powers. According to Kamui, when himself and Kanna merge into one being, the true nature of Shinbyeong is released.

Behind the Scenes
Kanna's name translates into "god of nothingness" (or "godless world"), which is a contrast on Kamui's name, which means "might of the gods".