Trying to understand why Sasuke's Rinnegan is actually special
Sasuke’s Rinnegan is the ultimate proof that Naruto’s power system eventually became a chaotic mess of rules that even the authors don’t seem to respect anymore. I’ve spent years living with the idea that his six-tomoe Rinnegan was a "premium upgrade"; essentially fusing his Eternal Mangekyou Sharingan and the Rinnegan into a single eye. The strongest argument for this has always been visual: those tomoe disappear when Sasuke is low on stamina, which strongly suggests a low-power mode where the Sharingan-part shuts down, leaving only the base Rinnegan behind. It made perfect sense, especially since he could fire off Amaterasu from that left eye without switching visual patterns; something that even Madara HAD to do in order to use his Sharingan abilities
The strict rule for Mangekyou Sharingans, which was literally carved into the official Databooks, is that Mangekyou abilities are eye-specific. In Chapter 464, Cee analyzes the fight and explains it clearly: the left eye spawns the Amaterasu flames while the right eye handles Kagutsuchi to manipulate them. If his Rinnegan wasn't this special hybrid, he technically should have lost the ability to summon black flames from that left socket the moment it transformed. But this is exactly where the canon starts sabotaging itself. If you look at Chapter 414 of Naruto and, more importantly, Chapter 54 of Boruto, Sasuke is clearly shown using Amaterasu with his right eye. In the Boruto panel, it’s particularly jarring because his Rinnegan had just been stabbed and was useless. This means he used the technique with the eye that, according to every established rule, was only supposed to be for shape transformation, not creation.
This basically nukes the "Supreme Rinnegan" theory that says a fusion was necessary to keep his powers. If he can just fire Amaterasu from his right eye now, then the ocular specificity that was the bedrock of the Mangekyou system has been pratically thrown in the garbage. Then there's the "off switch" issue. Madara, who awakened his Rinnegan through natural cell evolution, could revert his eyes back to a Sharingan or a normal eye. Sasuke can't; his is always active, which usually signals a transplanted eye that the body doesn't have the "genetic permission" to toggle (Nagato using Madara's rinnegan, or Kakshi using Obito's Sharingan are both great examples). Yet, his was a gift from Hagoromo, so his body should theoretically be more compatible than anyone else’s, since he was the current Indra's reincarnation.
Ultimately, we've reached a conclusion that allows for two answers. Either we decide that Sasuke reached such a god-tier level of mastery that he transcended the biological restrictions of the Uchiha, allowing him to manifest either Amaterasu technique through any eye, or we admit the (most probable) truth: the writers of Boruto and the end of Shippuden simply forgot the rules Kishimoto set in the 2000s.
I can't wait to hear you guys' opinion on this!