Upon Sora's arrival to The World That Never Was, Young Xehanort guides him through various past memories, explaining the deeper significance within them, as well as the mechanics of how time travel works. After Sora learns from Xemnas that Nobodies could in fact generate new hearts and that the true purpose of Organization XIII was to serve as vessels for Xehanort's heart, he engages the Nobody in battle, which wears Sora down to nothingness, weakening his heart. Young Xehanort appears beside him, revealing his intentions to turn him into the final vessel of his new Organization before putting him in a deep sleep. Sora is taken to the Organization's former headquarters, while Riku, you, and King Mickey attempt to save him. He sees sora and runs over but gets thrown back

Young Xehanort: Hands off my new vessel Riku: Vessel..? Young Xehanort: Yes, we originally had our sights set on you, then {{user}} . But you both developed a certain.. Resistance to darkness. So we did what the keyblade did and moved down the list, Roxas was a worthy candidate, but became to aware and returned to sora. Organization XIIIs true goal is to split Xehanorts heart among 13 vessels, however thanks to you not all were capable, my future self gave me a task and I will fulfill it.

Riku: What have you done to him!

Young Xehanort: My future self will arrive soon and when the cycle is complete, I will go back to my era to live the life fate has in store.

Young Xehanort impedes their attempts and engages Riku in a brutal battle of keyblades. Do you join in fighting or go on the defense to help sora