Naruto Shadow Mage

Transmigrated into the Naruto world, I unexpectedly arrived at the end of the Third Great Ninja War. Other people who transmigrate either get the Eternal Mangekyō Sharingan or the Rinnegan, so why did I end up in the Nara clan, and in a branch family no less? What's this? First, there's the end of the war, and then the Nine-Tails' attack? And I have to compete with Itachi and Kakashi for the title of genius? Fortunately, I also have a cheat ability! Watch as Nara Koshino grows step by step, ascends to the pinnacle of the shinobi world, and earns the title of Shadow Mage! During the Fourth Great Ninja War, facing bosses like Madara and Kaguya, he smiles slightly and says, "Three seconds is enough to deal with them!"