Zetsu

Zetsu (ゼツ, Zetsu) is a member of Akatsuki and one of Obito Uchiha's most loyal subordinates. The black half is known as Black Zetsu (黒ゼツ, Kuro-Zetsu), while the white half was known as White Zetsu (白ゼツ, Shiro-Zetsu).

Source: http://naruto.wikia.com/wiki/Zetsu

Background

White Zetsu was the first of the many artificial humans which were created by Madara Uchiha using a living clone of Hashirama Senju and the Demonic Statue of the Outer Path. Madara implied that Yin–Yang Release was also involved in the creation of White Zetsu and his clone siblings. Like the rest of Madara's creations, White Zetsu was tasked with intelligence gathering before he and another spiral-patterned clone were entrusted with looking after the rehabilitating Obito Uchiha. Over time, the duo became friends with the young Uchiha.

Black Zetsu being created.

At some point when Obito's rehabilitation was near completion, White Zetsu returned to the base and alerted Obito that Kakashi Hatake and Rin were being attacked by Kirigakure shinobi. When the spiral-patterned Zetsu offered to help Obito by encasing himself around the young Uchiha in order to enable him to leave the cave, White Zetsu served to guide Obito telepathically with the information he received from his clone brothers stationed outside. When they returned to Madara, White Zetsu assured him that no one had seen them and relayed information on what had happened after Konoha reinforcements had arrived, noting that Obito didn't kill Kakashi.
When Madara was on the verge of death, he infused a part of his will into White Zetsu, which created the second personality, Black Zetsu. This in turn made the complete Zetsu partially a clone of Madara, albeit weaker. Both halves later accompanied Obito to Amegakure to locate Nagato, who had unknowingly been given Madara's Rinnegan as a child. Zetsu then accompanied Obito as he approached the orphans, introducing himself as Madara Uchiha.

Personality

Accordingly with his two differently coloured halves, Zetsu has two personalities: the original White Zetsu being carefree and playful with a habit of teasing others, traits he shares with many of his clone siblings. Black Zetsu, however, is more serious and knowledgeable, being Madara's clone. In the Japanese version of the manga, Black Zetsu only uses katakana for okurigana and furigana, while White Zetsu uses kanji and kana regularly. This is often conveyed in the anime through their different voice tones. While the two halves sometimes differ in opinions and frequently converse with each other, they are still able to function as a single entity.
Zetsu is extremely trustworthy, obedient and loyal, being entrusted with Akatsuki's secrets and knowledge of Madara's Eye of the Moon Plan, which his white half believed to be beneficial to mankind. Because of his ties to Madara, Zetsu has apparently been working with Obito for some time, originally acting as Obito's superior prior to his induction into the Akatsuki. This is furthered by White Zetsu's long history with Obito when the boy was saved by Madara during the Third Shinobi World War. Though he annoyed Obito at first, White Zetsu eventually won the boy's friendship. Like his clone, White Zetsu believed Madara was a good man at heart and saw no harm in helping Obito without Madara's permission.
Zetsu's main role within Akatsuki is to function as a spy with other duties that were similar to those of a hunter-nin. He is also able to control his body and take part in the tailed beast sealing ritual simultaneously, which, in addition to being unique to him, allows him to act as a lookout while the sealing takes place. When an agent of Akatsuki, or possibly even a member, dies, Zetsu is sent to devour their bodies so as to not have their secrets revealed, which further adds to his nature as a half-plant creature. Zetsu is also the one sent to retrieve the rings of dead Akatsuki members. Due to the role he plays, Zetsu is the only member of Akatsuki to act without a partner on a regular basis. As such, he operated on his own, often moving between the different locations where the other Akatsuki members were located. This resulted in other members often reporting directly to him, rather than the figurehead leader, Pain. Zetsu would in turn report directly to Pain along with Obito, who took full control over the organisation after Nagato's death and treachery.

Appearance

Zetsu.

Zetsu is easily distinguished by the two large venus fly-trap like extensions that envelop his head and upper body, giving him a plant-like appearance. When his extensions are open and his head is visible, it is revealed that Zetsu has short green hair, yellow eyes, and that his body has two different coloured halves. His left side is completely white, while the right side is almost entirely black. The black colour does not cover his black half's entire body, as it only extends partially down his leg, which was originally his white half's right leg. Under his Akatsuki cloak, Zetsu wears blue pants and sandals. He also has both legs wrapped in bandages, which hide the area where his right leg's black colouring merges with his white foot.
Unlike White Zetsu, who possesses human-like facial features and a proper eye, Black Zetsu shows no visible orifices at all and only his iris is visible. Black Zetsu also has white dots along the edges of his body where the two halves meet; these are not flat markings, but rather protrude from his body, like little white bumps. White Zetsu also has unusually rounded teeth. In the anime, his fingernails are painted pink and his toenails, as seen at his début, are blue. He also wears his green Akatsuki ring, which bears the kanji for "sign of the boar" (亥, gai), on his right little finger.
When the two halves split apart, the plant-like extensions split and hang from the waists of both. Their clothes also split in half along with them, leaving each with one pant leg or half of an Akatsuki mantle, should they be wearing it. When they are emerging from the ground, their plant-like extensions surround the two halves in a circular pattern. The two have also demonstrated the ability to grow appendages to substitute for their missing half when split. Sometime after splitting, the two halves seemingly discarded their torn clothing.

Abilities

Zetsu merged with the ground.

Zetsu, as a whole, has yet to be seen in battle. The technique he has been shown using the most is Mayfly, which allows him to merge with the ground to quickly travel to a new location, though he isn't as fast as Obito's space–time travelling. This technique is ideal for Zetsu's function as a spy, as it erases his presence as well, and is an ability that both halves, as well as White Zetsu's clones, can use. In the anime, this technique allowed a White Zetsu Army clone to bury Deidara's underground mines. In addition to functioning as a single entity by communicating through their thoughts, Zetsu's two halves are able to split apart, which allows them to act independently. While separated, the two halves can extend roots underground to communicate with each other over long distances.

Zetsu physically splitting in two.

Being an artificial human, White Zetsu is able to survive without food or water and does not need to carry out normal human bodily functions. He can also telepathically communicate with other clones, as long as they are within a certain range. White Zetsu has mainly been seen using support abilities and Tobi has referred to him as not being a "front line" fighter. With his Spore Technique, White Zetsu is able to plant spores on the bodies of others, which are undetectable even to sensors and Kage-level shinobi. Once activated, these spores grow into a mass around the individuals they formed on by sucking out their chakra, which restricts their movements. The spores can also use this stolen chakra to replenish an ally's chakra supply by attaching themselves to him or her. Tobi had Zetsu attatch several of these spores to Sasuke Uchiha in order to monitor, and even assist him when necessary. In addition, White Zetsu is able to create and remotely communicate with near-identical copies of himself, which can be used as a special substitute by taking on the appearance and unique chakra of anyone White Zetsu touches. The clones are much weaker than the original and are therefore mainly used as decoys.
Black Zetsu has demonstrated the ability to "record" the things he sees, as he has stated that he recorded the battles between Sasuke and Itachi, and between Kisame and Killer B. He is also capable of showing these "recordings" through unknown means. Black Zetsu is also a very powerful sensor, as he was able to sense Naruto Uzumaki and Killer B as soon as they touched the ground upon leaving the Island Turtle, which was some distance away.

Nature Transformation

Black Zetsu creating roots from his body.

Because of his origin, Zetsu's genetic material is nearly identical to that of Hashirama Senju's, as seen from Shizune and Sakura Haruno's autopsy of one of the White Zetsu clones. Because of this, Zetsu is capable of using Hashirama's Wood Release, albeit on a much weaker scale. This has been most prominently demonstrated through Black Zetsu, who has been depicted transforming parts of his body into roots for offensive purposes during battle.