Polar particles

are a mysterious substance mentioned in one of the legends surrounding the Sage of Six Paths. Because of his time as a jinchūriki, the Sage developed a disease that caused his chakra pathway system to start deteriorating, threatening his ability to continue using chakra. The Sage traveled to the Land of Redaku and began charting the heavens in search of a cure. He eventually met Tataru Janmarū, founder of the Astronomy Research Institute.

One night, while the Sage was under Tataru's care, a meteorite passed through the sky. The Sage caught this meteorite, carefully cut it open with only his chakra, and used the polar particles found inside to heal his body. He hid some of the leftover polar particles in a lake near the Institute, leaving instructions about how to retrieve them in the guise of a game called Hoshinarabe. A thousand years later, Sakura and Sasuke Uchiha are able to acquire these polar particles in order to give to Naruto Uzumaki, a jinchūriki suffering the same disease as the Sage. Gigi also sought the polar particles for some unknown reason.