The following article contains major spoilers forNarutoandBoruto.

Narutois a story filled with great characters and, especially, an amazing world-building. Itachi Uchiha is definitely one of the most interesting characters inNaruto. He was initially introduced as a cold-blooded villain who had killed his own family, but we later understand that things were not as simple as they seemed.

An interesting feature of Itachi is that he is usually seen with his Sharingan active. While the Sharingan is powerful, users don’t usually keep it active; they typically only use it in battles. So why did Itachi activate this ability so frequently?

Naruto

Sharigan Can Make Up For Impaired Vision

The Sharingan is such a powerful doujutsu that it can apparently even make up for impaired vision— this is especially evident inBoruto; Sarada always takes off her glasses when she activates the Sharingan. This may be one of the reasons why manyNarutofans think that Uchiha clan members have enhanced eyesight (which actually would make sense).

Although it is not explicitly stated,Itachi may have kept his Sharingan activated so often because of his worsening vision. It is clear that he was almost blind when he died. While regular Sharingan probably wouldn’t worsen his vision, keeping it active often was probably costly in terms of chakra usage. It could also be related to the stress he was going through; Itachi also probably felt that he needed to be ready and keep his guard up by using the Sharingan.

Itachi Probably Overused Mangekyo Sharingan

While the regular Sharingan does not have major side effects, theMangekyo Sharingan, an evolved form of the Sharingan, canonically leads to blindness— andItachi probably overused this ability. As the Mangekyo Sharingan impaired his vision, he may have used the regular Sharingan to compensate for his worsening eyesight.

If he was under stress and wanted to be ready for any potential threat, his worsening vision would have made him more anxious. While he used the Mangekyo Sharingan to protect himself, it made him more vulnerable to enemies in the long run. Thus, the Sharingan could be a way to deal with this issue.

Many characters inNarutodie in battle, but Itachi is a rare exception — although the battles and the path he chose probably made things worse,Itachi had a terminal illnessthat ultimately killed him. He could have used the Sharingan frequently because of his illness.

It has never been revealed which illness it was, butfans have speculated about itbased on the symptoms, which include hemoptysis (the discharge of blood-stained mucus through the mouth) and chest pain (or other similar heart-related issue). These symptoms could indicate a variety of diseases, but some fans believe he suffered from microscopic polyangiitis (MPA), a rare autoimmune disease that can be deadly if not treated properly. While it is not terminal with treatment, it cannot be cured. MPA can cause eye irritation and diplopia, and it can rarely lead to retinal hemorrhage (and blood comes out of his eye in his battle with Sasuke).

If I had been open with you from the start… and looked you straight in the eyes and told you the truth, then I wouldn’t have had to stand before you, from above, as a failure, telling you all of this. So this time, I want to impart this truth to you… You don’t ever have to forgive me. And no matter what you do from here on out, know this… I will love you always.

— Itachi to Sasuke before dying

Even if Itachi had MPA, his blindness seems more related to the Mangekyo Sharingan, but MPA could have exacerbated the eye symptoms. Since the series never stated the name of the illness or provided clearer details, it could be something else. However, MPA seems like a good candidate.

Stress And Anxiety Should Not Be Overlooked

As mentioned before,Itachi was under high levels of stressand anxiety, which cannot be overlooked when trying to understand his behavior. He could have kept the Sharingan active frequently, even before overusing the Mangekyo Sharingan, because of everything he experienced and did. Therefore, it could be completely unrelated to his illness and partly unrelated to the Mangekyo Sharingan.

Itachi is a very complex character, and many things about him are still a mystery to fans. That’s how you know a character is well-crafted.

Narutoisavailable to stream on Crunchyroll, Hulu, Netflix and other services.

Naruto

A popular shonen anime based on Masashi Kishimoto’s manga, Naruto follows its eponymous shinobi’s journey as he goes from his town’s outsider to its hero.