That was a joke wasn't it? Blindness is the price for the super powerful techniques of the Sharingan, once you awakened those eyes, they will slightly lose their light as a result of their usage, this was always the case by those who were using this eyes, it's not the talk about a certain Jutsu. You can take a look at Amaterasu for example, which strains your eyes up to bleeding and pain, and the ability to delete the flames with your Mangekyou Sharingan strains your body even more [
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