The Eight Sign Seal



The Eight Sign Seal is a combination of two Tetragram Seals. Minato, after using the technique, has access to a "key" that can open or tighten the seal to his desires. This "key" was inscribed unto Gerotora and given to Jiraiya, who in turn left it for Naruto. The Eight Sign Seal is structured to naturally allow Kurama's chakra and Naruto's chakra to interact over time. This caused Naruto's chakra to grow in size and strength as a result, but also caused his body to naturally use some of it's chakra and chakra control to reject some of this chakra. As a result, Naruto's chakra levels were very poor. The seal also weaks over time, and needs the key to tighten when need be. As a result of the seal weakning, Naruto is able to access more and more of Kurama's chakra during battle, but without proper control, he will lose his mind and Kurama will take over. While the seal can be tighten, it seems that after the Fourth Tail was released, Naruto's seal was to weakened to be tightened. Minato repaired the seal when it broke against Pain, letting out 8 of the 9 tails. When Naruto managed to remove some of Kurama's Yang Chakra during their battle, his seal evolved into a Torii Seal, which is much stronger than his Eight Sign Seal. Naruto eventually opened his Torii Seal so he and Kurama could work together against Tobi.