Eye color: Yellow
Hair color: Green
Blood type: ?
Ring position: Right little finger
Partner: None or not yet introduced
Target tailed beast: ?
First cameo: None
First appearance: Chapter 234; Episode 134
Defining characteristics: Venus-flytrap like extensions around body, dual personality, skin color split into white and black halves, cannibal
Voice actor: ?
Zetsu (ゼツ, Zetsu?) is a mysterious missing-nin from Kusagakure. Not much is known about him, other than his allegiance to Akatsuki and his function as a spy. His head appears to be enveloped in a large venus flytrap. The right side of his face and body is black in color while his left side is white in color. He has pupil-less eyes similar in appearance to those of a Byakugan user and superior vision. He also has the ability to merge with the ground, trees, and other plants, allowing him to travel long distances fairly quickly. Akatsuki members have so far generally seemed to report to Zetsu as if he was a superior, though perhaps only because he is often acting directly on the instructions of the leader.
He seems to have a split personality, as the white half of his face speaks only in Katakana (which could indicate a robotic voice) while the black side uses Kanji and Kana. The two halves also seem to converse with each other, and occasionally differ in opinion, such as whether to allow Tobi to fill Sasori's place in Akatsuki.
The Leader often sends out Zetsu as a scout or courier. In addition to his role as a spy, Zetsu appears to function as Akatsuki's hunter-nin. He was sent to dispose of the corpses of those used for the leader's Shapeshifting Technique, as well as recover the rings of Sasori and Deidara. He performs the former function by devouring the corpses, which fits with his "venus flytrap" theme. His only known subordinate is Tobi, who is later promoted to full-fledged Akatsuki membership.
Zetsu's first appearance was after the fight between Naruto and Sasuke at the end of the first arc, which he observed in secret. He was also responsible for warning Akatsuki of the positions of the approaching Team Kakashi and Team Guy during their extraction of Gaara's tailed beast.
The leader dispatched Zetsu to recover Sasori and Deidara's Akatsuki rings since they were both expected to be killed. This highlights some significance in the rings, since Tobi takes Sasori's ring and asks Zetsu if he can join Akatsuki in Sasori's place. The human-sounding half of Zetsu scoffs at the idea, but the robotic half seems intrigued. Given that Tobi is now a member, it would seem the latter half won out.