The adventure through Yen Sid's vault puts the destiny trio through a gauntlet of the Disney worlds from the previous games. After finishing the last they reach a lush field with a solitary tree at its center. Beneath it is Sora's body, as well as the ever grim Yen Sid. Finally face to face with the sorcerer, Sora engages in a heart to heart.
He tells him about how he saw what happened at Scala ad Caelum and understands why he thought sabotaging Sora's life would prevent that. But regardless of all of that, what Yen Sid has done is wrong, and he's causing Innocent people to suffer needlessly.
The sorcerer is surprisingly unfazed by this. He already knows that his mistake has doomed the universe, and nothing matters anymore. At the same time, he admits that there was a secret darkness behind everything he did. On a fundamental level, Yen Sid just doesn't like Sora. Despite the boy's irrevence and lack of birthright, he was the one to be chosen by destiny (not Riku or Kairi).
Having had enough of the sorcerer, Riku declares that he full-heartedly disagrees and initiates the battle.
Despite Yen Sid's immense magical prowess, Sora and his friends win the day. With his last barrier obstacle defeated Sora returns to his body. With a little help from Riku and Kairi the boy is brought to his feet, yet is quickly knocked back down by a suddenly manifested Master of Masters.
"Well me, it looks like you finally did your job" the man taunted.
Acting on impulse Riku and Kairi strike-out, succeeding only in getting their weapons caught by the master bare-fingered and are summarily tossed down alongside their friend.
"Honestly guys, attacking me after everything we've been through? I'm offended."
"Then what do you call what you're doing!?" Sora demanded as he struggled to his feet.
"Plan C" replies the master, revealing Luxord's wild card that he just pinched off of his younger self. "You see, keeping the universe from collapsing has been like an endless, all-or-nothing, poker game. With such high stakes I got used to setting up an ace up my sleeve. Or in this case, a king". Raising the gambler of fate's card aloft he summoned a crown to its surface, and the universe's collapse came to a sudden halt.
Back at the survivor's battle, the heartless hoard suddenly froze in place. Despite their weariness the remaining champions of light could not help but be thrown off by this development. Before anyone could voice their concern the barren world around them began to shift.
Like a rewinding movie the barren landscape re-integrated and disintegrated itself into countless bygone cities. First into the cable-strewn skyline of Scala ad Caelum, then into the twisting streets of Day Break town. On and it went until finally settling into the dark and rainy streets of Tokyo, and in the park center, the Master of Masters and the stunned destiny trio.
"Now without further adieu-" the man declares as he summons the kingdom key. "Let's bring it on home". Before anyone could react the Master tossed the playing card at his younger self and unleashes an unsealing beam through it, striking Sora straight in his heart.
A shockwave knocks away the boy's companions, and accompanied by the boys screams the crowns of his past journey escape one by one. The objects begin to orbit him, rotating faster and faster until flying into the sky and encircling the moon. Then, with a Nova of light, the original Kingdom Hearts is born...
Before the survivors or heroes can recover, the senior Sora slumps his unconscious junior over his shoulder. "Thank you all for being a wonderful audience, but if you'll excuse us we are late for a very important date." At this point Riku and Kairi regain their footing and beg him not to do this. With a melancholy voice he replies "sorry guys, but only one Sora can win this game... I would ask that you don't follow me, but I know that you'll try anyway."
Turning skyward, the Master of Masters gave his students one final assignment. "Invi, Gula, Luxu, Ira... Aced... give me a little more time..." On queue the surviving keyblade master appeared in full battle attire. Forming a line between him and the recovering heroes, their mentor leapt into the sky and flew towards Kingdom Hearts (back to where everything will ultimately begin).