Re: Tobi can't possible be Obito
Several reasons why Tobi cannot be Obito
1) The sudden leap in ability. When Obito died, he was a Chuunin. From Kakashi's age, we can infer that Kakashi was 13 or 14 when Obito died (Kakashi is 26-27 at the start of Naruto, and he was 13 when he became Jonin. At most, nine months pass between the Kannabi Bridge mission and Naruto's birth, if Kushina got pregnant only after the mission. Or it could have been as short as a week for all we know). So, at most, Obito had only nine months to somehow jump from Chuunin rank to fighting at least on equal terms with the Fourth Hokage. Given from what 599 tells us, Obito was jealous of Kakashi outstripping him. If Obito managed to be equal to the Fourth...why is he jealous?
- Side note to that fight with the Fourth. In a battle, especially ninja battles, you're supposed to use any and all tricks necessary to win. If Tobi was Obito, wouldn't he have pulled off his mask and said "Hi Sensei! Great to see ya!" so as to distract Minato, get him to pause for a second?
-Obito clearly died from the cave in. He has a ton of huge rocks on top of his body. In fact, it's already hard to believe he survived long enough to say goodbye to his team-mates and to give Kakashi his eye. Even if somehow the rocks were just the right shape and he was in just the right position to only be trapped but not actually harmed by the rocks...why would his team-mates then leave him alive to starve to death? If he was only trapped and not harmed by the cave-in, they would have granted him a merciful death, to spare him the agony of starving.
-Obito had only awoken his Sharingan for the first time that mission. No way that after the cave-in, he somehow used Kamui to save himself.
-Even if he did somehow use Kamui...what possible motive does he have to become the villainous mastermind behind everything? From the montage we see in 599, Obito at most is jealous of Kakashi and pissed off at him. That's it. At his death, he died with a smile on his face, willingly giving up his eye to his friend. If he was actually evil...why willingly give up his eye? Why, if he survived, didn't he go back to Konoha? Why, if jealous of Kakashi being better than him, give him an eye that would only serve to make him even better? If he survived, why do everything he did, instead of going back to Konoha and beating the living crap out of Kakashi?
-As for the possibility of it being Obito's body that is being controlled or possessed in some way (say via a Yamanaka-esque mind control jutsu, or through him being resurrected with Edo Tensei), two things are wrong with that. First, this implies a FOURTH hidden character (first hidden character was the leader of Akatsuki, later revealed to be Nagato/Pain. Second was Tobi, whom at first was said to be Madara Uchiha. Third was Tobi again, once it was revealed Madara was a separate individual) So now, close to the end of the manga, there's a possibility of a fourth hidden character? Imagine if, say, in Harry Potter and the Deathly Hallows, during the Battle of Hogwarts, it was revealed Voldemort's body was being controlled by his third cousin twice removed? In a piece of literature, you don't reveal at the very end that your main villain is actually somebody else, whom the audience has never before seen.
The second problem with that is...why Obito? Why control/resurrect Obito? He was a no-name ninja. His only claim to fame was that his sensei became Fourth Hokage. He didn't accomplish anything and had no notable skills, so why use Obito to fight against the Fourth a year after his death? This would be somewhat like Kankuro choosing to use a basic puppet to fight against a Kazekage, rather than say Sasori's puppet body. Especially if somehow his controller/possessor knew before Obito's death that Obito's eyes would develop the Kamui power. How would they have known?
Lastly...what's up with 599 showing Kakashi taking the Chuunin exam at the same age as Obito and Rin? He didn't. The official databooks say he became a Chuunin at age six, having graduated as a Genin at five. So Kakashi had no business at all even so much as being part of the same graduating class as Obito and Rin.