With the release of Sasuke Retsuden chapter 1 on October 22, Naruto fans were excited to see a manga focusing on Sasuke's mission outside the Hidden Leaf Village. Although Sasuke is the focus of this manga series, the plot currently revolves around Naruto, more specifically around Naruto's chakra illness.
The first scene in Sasuke Retsuden has an ill Naruto trying to stop Sasuke from going to the Land of Redaku. Kakashi had already gone to the village searching for information to save Naruto before, but the Hidden Leaf Village hadn't heard back from him. Considering Naruto's growing health problems, Sasuke decided to search for some answers on his own. Thus, Sasuke Retsuden will follow Sasuke in the Land of Redaku trying to find a cure for Naruto's illness.
Disclaimer: This article contains spoilers from the Sasuke Retsuden light novel.
Sasuke Retsuden: What caused Naruto's illness?
Naruto's illness was apparently caused by his Sage of Six Paths powers, given to him by Hagoromo Otsutsuki himself during the Fourth Great Ninja War. During the war, both Naruto and Sasuke had near-death experiences when Hagoromo Otsutsuki decided to visit them in a different plane, where he gifted both of them with powers. Sasuke was given the Rinnegan while Naruto was given access to the chakras of all nine tailed beasts.
Having access to such an enormous source of chakra is what caused Naruto to become ill as he was exposed to it for about 16 years. Due to the prolonged period of exposure to such a massive chakra source, the chakra within Naruto's own body was negatively affected, causing him to suffer from spasms and lose his balance.
While the reason for this hasn't been revealed yet, according to Kurama, the Sage of Six Paths also suffered from the same illness. However, Hagoromo Otsutsuki was able to find a cure for it during his journey through the Land of Redaku.
What is the cure to Naruto's illness?
During his journey to the Land of Redaku, Sasuke met a woman named Lyla, whose mother seemed to have some idea about the Sage of Six Paths. When he finally met her mother, Kail, she proceeded to look into the Book of Yoru, which seemingly contained a lot about Redaku's history.
However, upon realizing that certain pages had gone missing, she mentioned how there were texts retracing back to the Sage of Six Paths' time in the Tatar Observatory, which led Sasuke to his next location in his search for a cure. While Sasuke spends his time in the observatory, he finds some new intriguing mysteries surrounding the Land of Redaku.
Based on the light novel series, the Sage of Six Paths found a way to heal himself after he split a looming meteorite. The polarized particles from the meteorite healed Hagoromo Otsutsuki, returning his condition to normal.
The cause for such phenomenon could be the origin of Otsutsukis, as they themselves are otherworldly beings. Being part human and part Otsutsuki, Hagoromo Otsutsuki must have been vulnerable to this kind of illness, which could have only healed after he was exposed to the polarized particles of the meteorite. Following his recovery, the Sage of Six Paths inscribed the details to obtain such polarized particles in a document hidden deep within the Observatory.