The Serpent's Pupil (大蛇の瞳孔, Daija no Dōkō) is episode 113 of the Naruto: Shippūden anime.
Orochimaru's current body is at its limit, and the time to change bodies draws closer. Kabuto tries to ease Orochimaru's pain through medicine. Kabuto notes that Orochimaru's body is at its limit and Orochimaru is holding on through sheer will. Orochimaru and Kabuto reminisce about the steps taken and all that has happened between the Invasion of Konoha and now. As Orochimaru's condition becomes worse, Kabuto realises that an increased dosage is necessary. Orochimaru is excited at the thought of finally acquiring Sasuke's body and with it the Sharingan, he begins thinking of his journey of trying to acquire the Sharingan, from his failed attempt at Itachi, to everything he's done to acquire Sasuke. He notes that Sasuke is truly a genius, and nobody but him could have understood his thirst for power, and nobody could have trained Sasuke better than him. He notes that with enough time, Sasuke might even surpass Itachi. Orochimaru then notices that there is someone outside his door, and commands him to show himself. Suddenly a lightning based chakra pierces through the door and head's towards Orochimaru. He blocks the technique with his forearms. The door is slashed and Sasuke enters. Sasuke explains to Orochimaru, about how pathetic Orochimaru is compared to the Uchiha's. A battle begins where Sasuke looks to have the advantage until Orochimaru switches to his true form. As Orochimaru attacks Sasuke, he switches to his Cursed Seal Level 2, and prepares to finish the battle.