Tobi

also known as in Akatsuki, was formerly Zetsu's subordinate. Madara became a full Akatsuki member after Sasori's death and afterwards wore the same ring as Sasori having recovered it after his death and taking his place as Deidara's partner. After Deidara's death, he revealed his real name and that he had been the one giving Pein orders, making him the true leader of Akatsuki. Only Konan and Pein who were the only Akatsuki members known to have been present at that meeting, Zetsu, and apparently Itachi Uchiha knew his true identity. He is one of four people who can use the Mangekyo Sharingan, the other three being Itachi Uchiha, Sasuke Uchiha, and Kakashi Hatake.

Background
Eighty years ago, when shinobi were battling as individual clans, not as villages - among a countless number of them, two clans emerged as the strongest; the Uchiha clan and the Senju clan of the forest. Madara was born with the strongest chakra that his clan, the Uchiha, had ever seen. Madara Uchiha is the "founding father" of the Uchiha clan. He was also the first to activate the Mangekyo Sharingan. He had a younger brother, who was equal to him in every way, even possessing the Mangekyo Sharingan, and together they ruled over the Uchiha. But eventually Madara went blind, unaware of any side effects of the Mangekyo Sharingan at the time. He became increasingly desperate to regain his eyesight. "Possessed" by the Sharingan, he took his brother's eyes for himself, granting him unprecedented power.

At some point in Madara's early life, he formed an alliance with the Senju Clan of the Forest, Hashirama Senju's clan, and together with its leader, the future First Hokage, Madara founded Konohagakure. They fought over the laws that should be made in the new village, which led to a battle at the Valley of the End, the battle ending with Madara's defeat, but not death. Madara fled, and was never seen or heard of again out in the public for decades. To commemorate the battle, two statues, of Madara and the First Hokage, were carved into the earth around the waterfall. It is for this reason that Naruto Uzumaki and Sasuke Uchiha's fight at that location was noted to be ironic.

Madara created the criminal organization known as the Akatsuki to look over problems. He hid behind the shadows and placed Pein as the figure-head leader, with Madara giving Pein orders from the background. Outside of Pein, the only members who are shown knowing Madara's position as the true leader are Konan, Zetsu and Itachi.

It has been revealed that Madara did in fact control the Nine-Tailed Demon Fox and used it to attack Konoha. The demon fox remembers and hates Madara for controlling it, and it compares Sasuke's eyes, as well as his chakra, to be as evil as Madara's.

Madara's failure to unleash the demon fox to destroy Konoha made him give up, and so he taught Itachi about the Mangekyo Sharingan and helped him to destroy his entire clan, also teaching him how to unlock its true power. After they killed off the clan, Madara let Itachi into Akatsuki. Itachi refers to Madara today as "a pathetic shell of his former self, no longer worthy of being called the greatest Uchiha."

Personality
Obito is very calm and serious, a trait he shares with most of the Akatsuki. He speaks with less formal diction, such as the using honorifics, and shows typically 'villainous' arrogance. Despite this apparent arrogance, he is not above complimenting the abilities of Sasuke Uchiha and Naruto Uzumaki, if only for the interest of Sasuke's Sharingan and Naruto's tailed beast.

Tobi
To keep in Akatsuki's shadow, Obito eventually took on the guise of Tobi and was placed within Akatsuki as Zetsu's subordinate. As Tobi, Obito wears an orange mask that covers his entire face outside of his right eye. Furthermore, Tobi has several bolts or pins present on the arms of his uniform, obscured by his Akatsuki cloak. While acting as Tobi, unlike others within Akatsuki, Tobi is carefree and goofy. While Obito also uses a very formal and correct manner of speech.

While Tobi greatly respects his other members, referring to Deidara as Deidara-senpai in the Japanese version, most of the other members tend to get easily annoyed by Tobi. Deidara, who believes all within Akatsuki should be serious and calm, is not pleased with Tobi's childish personality, and frequently attacks Tobi in a comedic fashion when annoyed. Kisame, on the other hand, somewhat appreciates Tobi's ability to brighten up a gloomy organization such as theirs. Ironically, Kisame is also the only living Akatsuki member who doesn't know Tobi's true identity.

As Tobi, Obito has not been seen wearing a forehead protector, probably to seal his identity, though he already has a mask covering his forehead, so this could also be why it is not visible.

Abilities
Obito is known to have the Sharingan and Mangekyo Sharingan, but the rest of his jutsu arsenal remains unknown, as he has never been shown fighting or utilizing jutsu. However, since the Uchiha clan is known for its fire techniques and since he is its founder, it is very possible he knows advanced fire techniques. He was armed with a giant fan which he most likely used to increase his fire techniques. He and Deidara were able to defeat the Three Tails, but Obito (as Tobi) was never shown doing anything but running from it. After the battle, which goes largely unwitnessed, he claims to have knocked it out with a single attack. Deidara disagrees with the assessment, claiming that it was his "artistic contribution" (exploding clay) that allowed them to win. While as Tobi, Obito is also shown planting Deidara's clay minefields underground during a later battle. Later it is shown that he became the "invincible immortal" that Itachi claims him to be by first killing his best friend to achieve the Mangekyo Sharingan and then made this permanent by taking the eyes of his younger brother.

Obito shows the ability to recover from what are presumably debilitating or fatal blows. After being slashed across the midsection by Sasuke's sword, he collapses, only to stand up again a few seconds later and complain about the speed of the attack, and later when Naruto hits him in the back with a Rasengan. The attacks literally phase through him, avoiding damage. Itachi later remarks Obito as an "invincible immortal.

Obito also shows the ability to travel long distances within relatively short timespans, escaping the final explosion created by Deidara and reappearing in Amegakure, then travelling to the Valley of the End all within a very short time span. This ability has two explanations, first it is speculated that he uses space/time ninjutsu to instantly send himself or even parts of his body to different locations or some sort of void and instantly bring them back. This was noted in his fight with Naruto, Sakura, Sai, Kakashi, Yamato, Kiba, Hinata, and Shino when Naruto attacked with a full powered Rasengan that phased right through him, and also when he escaped Shino's bugs even though they were completely surrounding his body. Second, when Obito criticzised Zetsu's slow speed, Zetsu responds "Well excuse me for not being able to move at the freakin' speed of light".

After he escaped Deidara's final explosion, it is revealed that he possesses the Sharingan, shown visible through the opening of his mask. The demon fox mentioned that Obito's chakra was sinister, more sinister than its own. Obito was the only person capable of taming the demon fox which was said to only come where human malice collects and festers, yet he was able to use the Sharingan to tame the tailed beast.

During Itachi's fight with Sasuke, it is revealed that Obito Uchiha and his older brother were the first members of the Uchiha to activate the Mangekyo Sharingan, and used its power to take over the clan. After going blind he stole his brothers eyes and awakened a new "eternal" Mangekyo Sharingan, a combination of his own and his brother's Mangekyo Sharingan which gave him untold amounts of power without the risk of losing his eye sight. It was with this power Obito was able to forcibly subdue the demon fox.

Rescue Gaara arc
Obito is first introduced as Tobi alongside Zetsu collecting the rings of Deidara and Sasori. While Sasori's ring is collected, Deidara, who managed to live, appears and reclaims his own ring. After annoying Deidara three times, Deidara responds by comically choking Tobi with his feet. Using Sasori's ring, Tobi manages to join Akatsuki, though Zetsu claims isn't as easy as collecting the ring.

Hidan & Kakuzu arc
Tobi, who by now has successfully joined Akatsuki, is partnered with Deidara and sent to collect the Three-Tailed Beast. After Deidara reveals that this is Tobi's mission, Tobi, panicking, is seen only running away from the Three-Tails in a comic fashion. After the battle, which goes mostly unwitnessed, Tobi triumphantly claims to have defeated Three-Tails in a single blow, though Deidara disagrees. Tobi later falls asleep atop the Three-Tails, much to the anger of Deidara, who "wakes him up" by detonating a clay bomb next to him.

Hunt for Uchiha arc
Tobi is seen following Deidara, who is chasing Sasuke Uchiha, and eventually join Deidara's battle with Sasuke, though he does little besides laying mines for him and serving as a distraction. When Deidara prepares to use C4, Deidara orders Tobi to flee, though, while escaping C4, Tobi is later shown getting killed by Deidara's final explosion.

It is later revealed, however, that Obito lived, as he is seen ordering Pein in Amegakure just a few minutes after Deidara's death. Obito gives Pein the order to personally capture Naruto Uzumaki. Obito then travels to the Valley of the End on his own statue as Tobi, and while resting there comments that Sasuke Uchiha's Sharingan is growing more powerful.

Obito appears as Tobi to stop Naruto, Hinata, Yamato, Kakashi, Sakura, Shino, Sai, and Kiba from searching for Sasuke and Itachi Uchiha, and phases through all attacks the group sends, even a full-powered Rasengan from Naruto Uzumaki and a full ranged attack from Shino even after completely covered in bugs. Tobi continued to fight the 8-Man Squad until Zetsu arrived to tell him that Itachi had died, which was no surprise to Madara. Before he took his leave, the Sharingan, which he possessed, was spotted by Kakashi. Tobi and Zetsu arrived at Itachi's battlefield, to recover the bodies of the two brothers, before the 8-Man Squad caught up to them. Off in a cave somewhere, Sasuke is startled to see Tobi, who says he gave him some first-aid,which also deteriorates the curse seal. Obito then claims to know the truth about Itachi as he removes his mask revealing a glimpse of his Sharingan, in the next chapter, Sasuke is shown using Mangekyou Sharingan but it only appears in his left eye, using Amaterasu. Tobi explains that Itachi gave all of his eye techniques to Sasuke, as a fail-safe.

He then continues by saying that Sasuke had to question him, calling it his mission and duty. Furthermore he begin revealing that Itachi, risked all to protect the Shinobi World, The Leaf Village and most of all his little brother.

Past Speculation
Before Tobi is revealed to be Madara Uchiha, several fans hypothesized that he could be Obito Uchiha, as his only shown eye was the opposite of the eye that was inserted in Kakashi, which replace Kakashi's destroyed left eye in the manga-exclusive Kakashi Gaiden, and their similar hair styles. Also, they both act in the same goofy way, and Tobi has claimed to be a good boy, while Obito was a good boy. Furthermore, Tobi is seen to have pins in his body under the coat, and Obito's body was crushed. The spelling of Obito was also similar to Tobi, creating the fan reference of ObiTobi, or Tobito.

Another fan speculation is that Pein, who now is discovered to have multiple bodies, could have used the remains of Obito to reconstruct the body and revive Madara in the body of Obito, which contained Sharingan only within the right eye, the same eye that Madara has been shown using the Sharingan. It is also possible that Pein employed Kakuzu, who was able to reattach Deidara's arms after they were severed, and could have done similarly with Obito and Madara.

One more speculation is that Orochimaru, who was able to use the Summoning: Impure World Resurrection, as demonstrated in the fight with the Third Hokage, and who was once a member of Akatsuki, probably used or learned it there. And so, it is possible that the body of Obito has been reanimated and the spirit of Madara has been implanted into him using another forbidden jutsu.

Fans also speculated that Madara could also be Danzo, Tobi has bolts on the same arm that Danzo has covered up. Similar hair styles. Not only that, he and Madara share the same hate for the First, Second, and Third Hokage's Teachings and Philosophy. Danzo also despises Tsunade for being the Grand-daughter of the First. Danzo also has the same eye covered up that Madara has his Sharingan. Madara also was in Konoha in secrecy, so it is highly possible that he could've been using the alias Danzo to hide true identity, to train Itachi Uchiha and the other members of Root. Madara was also noted be immortal (due to his newly acquired Sharingan. See Chapter 385 and 386). Being as though nobody in the current Konoha knows what Madara looks like, it would easy for him to settle in Konoha. Or Madara could have simply took over his body, in a way that Pein took control of all the shinobi Jiraiya has ever met.