"The Blue Beast vs. Six Paths Madara" (碧き猛獣VS六道マダラ, Aoki Mōjū VS Rikudō Madara) is episode 418 of the Naruto: Shippūden anime.
As Orochimaru and his team reach Sasuke, they realise that the unknown chakra signature is that of Kabuto. Since Kabuto has assimilated other people into himself, his chakra signature has become unknown, explaining why Karin could not identify the person near to Sasuke. Kabuto explains that he has decided to save Sasuke, after coming to realise who he was, thanks to the Izanami. Elsewhere, Guy releases the Gate of Wonder, which fails to damage Madara. Knowing that the Seventh Gate failed, Guy realises he must use the Gate of Death, which he knows will kill him. He remembers his time with his father, where he failed to graduate and decided to run 500 laps in order to enter the Academy as an alternate student. However, Guy is unable to finish running 500 laps and ends up passing out while the Third Hokage watches him from the window of the Academy. As Guy apologises to his father only to be scolded for not having faith, Guy becomes frustrated with his father being mocked and attacks two older ninja, only to end up being brutalised. He's saved from further harm by Kakashi taking out the older ninja. After being saved by Kakashi, Guy watches him leaving with his father.