A gentle song begins as Melanie, Willow, Scarlet and Aya are shown lying all besides one another sitting in a circle. "The One and only has come and there can only be one! And at Last I am Here!" Willow, Scarlet and Aya fade away as Melanie is shown sitting up as she suddenly was on the Destiny Islands beach. Melanie turns to look behind her at the sound of her name. Riku held his hand out with a smile. Sora and Kairi stood beside him with smiles on their faces. "Why can't I even breathe? Standing in the wreckage." Melanie reaches for Riku's hand before the ground caves out beneath them. "The rain, a lullaby and so I close my... eyes." Sora is shown with Donald and Goofy fighting off Heartless together before light flashes and Roxas, Axel and Xion are shown standing together as they faced away from Aya who turns to look back at them before they fade away and she laughs as she talks with Roxas, Pence, Olette and Hayner. "Within this world if you wish to live another day! You must disguise as a flower that will captivate!" Light flashes and Willow's flower pod is shown before Willow is shown floating inside before Ventus is shown sitting on his chair as Aqua, Scarlet and Terra floated like ghosts before they vanish into black smoke. Scarlet is shown reaching for Terra before she fades away. Riku is shown standing in his regular form before he's shown in the Organization outfit facing away from himself. "You, I want to believe! But I cannot believe!" Disney characters are shown as Melanie, Scarlet, Willow and Aya are shown flashing across the area like a ghost. "I'm powerless! I'm meaningless! Like every scar! But as I cry, tears fill inside right through my heart!" Kairi is shown standing on the beach alone as she stares out into the ocean waiting for her friends to return. "Through it all, I can hear someone whispering, 'come near'! All that I miss, it's infinite!" Xehanort is shown at the top of a rock with his organization members around him before Terranort is shown with a smile on his face and Scarlet is shown floating behind him with a sad look on her face. "And so I see! Tomorrow's come with a new sun waiting for me! The One and only has come! And there can only be one! And at Last... I am here!" Queen Minnie, Daisy, and King Mickey are shown standing together. "There is a part of me that wants to forgive you!" Riku and Sora are shown fighting off Xemnas. "But I will not forget – I can't understand...yet." Riku is shown reaching for Melanie with Sora whose shape changes into Ventus and Roxas slowly as Willow and Aya are shown over Melanie before Melanie's eyes open and she grabs Riku's hand. "Within this world if I were to live another day! I must learn this song and quickly learn to play along!" Light Flashes and Kairi is shown reaching for Sora as the two were being separated by a rift. "If I want to believe! I just need to believe!" King Mickey is fighting off enemies with Riku in order to get to Melanie. "Freedom's a lie – Even so I must cross that line!" Light Flashes and Aya is shown as a child laughing with Lea and Isa before light flashes and Axel is shown standing in front of Melanie before he looks over his shoulder to see Saïx and the rest of the first Organization staring at them. "I'll scream it loud – Barren, I shout 'I'll make it mine'!" Light Flashes as Willow, Ventus, Aqua, Scarlet and Terra are shown laughing together before Willow and Ventus fall back asleep just as Terra turns into Terranort, Scarlet gets bound in chains and Aqua is absorbed in darkness. "And so I turn away from the truth that's in my way!" Light Flashes and Willow, Scarlet, Melanie and Aya are shown standing together with their backs to one another as they stand in a circle. "Defy the gods, despite the odds! I'll find that light! Something so pure – I'll search the world into the night!" Ventus, Terra and Aqua appear in front of Willow and Scarlet before Roxas, Axel, and Xion are shown standing in front of Aya. "The one and only has come and there can only be one! And at last..." The two groups fade away as Willow, Scarlet and Aya are shown turning into three floating hearts that enter Melanie and she closes her eyes as she held her hand against her chest before she opens them to find Riku, Kairi, Donald, Goofy and Sora smiling at her while Riku had his hand outstretched to her. "I am here!" Melanie reaches towards Riku to take his hand before light flashes and the title is shown.
At the center of where the Keyblade War was fought, Terra arrives first. He's joined by Aqua who demands answers. She looks at him and then looks down. She looks back up ready to speak.
"I was told the Master was struck down..." Aqua says and Terra gasps in shock.
"Yes... that's right." Terra says, "I was stupid and helped Xehanort do it."
"You also helped him get Willow's body." Aqua announces.
"What? No, I was trying to save her. I was intercepted getting her to Master Yen Sid's. She was stolen from me." Terra defends himself.
"You were taking her Master Yen Sid's?" Aqua asks.
"It'd be the only place... out of Xehanort's reach." Terra explains and Aqua nods. Aqua was glad to hear that Terra tried to save Willow.
"The Master – he tried to hurt Ven and Willow was going to die trying to protect him." Terra announces.
"That sounds like something she'd try to do." Aqua replies.
"I only fought because I wanted to protect them." Terra says, "But I was tricked. Xehanort set the whole thing up... all so he could awaken the darkness inside me." Aqua and Terra get quiet for a few moments and then Terra looks at Aqua.
"You were right, Aqua – and so was the Master." Terra says, "I did need to be watched. I went astray – but no more. I'm here to save Scarlet, I'm going to purify the darkness from her body. If you'll help me. Then we'll rescue Scarlet and Willow together." Aqua gets quiet again and she gets tears in her eyes.
"What else is darkness but hate and rage?" Aqua asks, "Xehanort is feeding the dark fires within you – making you fight. You'll go astray again. Tell me – how does that honor our Master's memory, Terra?" Terra gets quiet and he looks down. Aqua sniffles as she places her hand against her chest.
"I can't sense Willow anymore. She's no longer with me." Aqua announces. Ventus approaches them and hears Aqua speak.
"That's because she's with me." Ventus says as he approaches. Willow appears like a ghost beside Ventus.
"Willow... you're see through. You should go to your body." Aqua breathes out in shock.
'I can't. I can't leave you all.' Willow's voice says, 'I can't... I can't leave Ven. I... I almost lost you all once... That's why I'm like this.'
"Pure light... but can still feel loneliness." Aqua says as she looks down.
"Xehanort wants me and Vanitas to fight and make some kind of χ-BLADE. But the Master said we can't let that happen and he tried to destroy me for it. He was going to take down Willow and Terra because they were in his way." Ventus announces. Willow looks at Ventus then at Aqua and Terra.
"χ-BLADE?" Aqua asks, confused.
"I still don't know exactly what it is. But... It scares me to death. Even just the thought of it." Ventus explains.
"Relax, Ven. We're here and we're gonna take care of you." Terra declares.
"Yeah." Aqua agrees.
"I may have to fight Vanitas after all." Ventus says, "If I do, guys... I want Willow to leave my heart and I want you guys to—"
"The five of us can never be torn apart, all right?" Terra says, "I'll always find a way. Just like we're going to find a way to free Scarlet."
"I'm asking you, as a friend... Just... put an end to me." Ventus says and Willow's eyes widen in shock as her hand goes to her mouth. Aqua and Terra also gasp in shock. The wind picks up and Willow gasps.
'My body!' Willow's voice says as Vanitas appears carrying Willow's sleeping body over his shoulder.
"Behold... These lifeless keys used to be full of power – united with the hearts of their masters. On this barren soil, Keyblades of light and darkness were locked in combat... as a great Keyblade War raged. Countless Keyblade wielders gave up their lives all in search of one, ultimate key... And it will soon belong to me..." Xehanort says and points at the group, "χ-BLADE!"
"Release Willow now!" Terra demands.
"Not just yet." Vanitas replies.
"I'm not ready to end her yet." Scarlet states, appearing beside Vanitas and Xehanort.
"Scarlet..." Aqua breathes out. Scarlet holds out her hand and a keyblade sporting black butterflies, wound with thorns appears in her hand. It was nothing like Master Juniper's Butterfly Keyblade. It was the Dark Dream Blade. The group gasps in shock.
"By the end of this, Terra, we will be together." Scarlet announces, "You in darkness as my Knight of Darkness and our worthless friends extinguished." Scarlet holds her weapon towards Willow. Ventus gasps in shock. The group activates their armor so that they'd have some protection in the fight to come. Ventus goes to rush forward but Terra stops him. Terra rushes forward but Xehanort uses darkness to lift the ground up and create a wall that Terra crashes into. Xehanort lifts himself, Vanitas and Willow's body higher. Vanitas rushes to attack Ventus. He throws Willow at Ventus and Ventus gasps as he and Willow's body goes flying back.
Vanitas attacks Terra and Aqua. Aqua gets thrown to the ground and her helmet falls off. Ventus runs over to Aqua while carrying Willow in his arms.
"Aqua! Are you alright?" Ventus asks.
"Yes, but we're sitting ducks here with Willow's body!" Aqua exclaims before she stops Vanitas from flying around attacking. Ventus sets Willow down and places his hand gently against her cheek. He stares down at her.
'Please leave me, Willow. You'll be safer in your own body.' Ventus's thoughts say as he looks at her.
'I can't just leave you.' Willow's voice says.
'Do it!' Ventus's thoughts say and he rushes up and attacks Xehanort after Terra does. Aqua looks over as Scarlet is shown standing in front of her. An ankle bracelet that Scarlet kept on her ankle makes a clinking sound.
"And now I get to snuff out Aqua's light." Scarlet explains.
"You're not Scarlet." Aqua explains.
"You're right, I'm something better! I'm who I'm supposed to be! The Princess of Dreams!" Scarlet exclaims. Aqua and Scarlet begin fighting. Scarlet and Aqua went back and forth, each equally matched. Scarlet had spent all her life watching Aqua learn how to fight, after all. Aqua gets the upper hand on Scarlet and Aqua hits Scarlet with a powerful attack and Scarlet gasps in shock.
"W-Why would you..." Scarlet asks. Ventus and Terra gasp in shock and look back. Scarlet begins to fall back. Her body vanishes into a dark corridor, disappearing completely. Xehanort had managed to dodge before he grabbed Ventus by Ventus's helmet.
"VEN!" Terra yells. Terra rushes to help but gets thrown down by Vanitas. Aqua looks up and her eyes widen. Willow's scream is heard before a bright light is shown exiting Ventus's body from Ventus casting her out. Ventus echoes Willow's scream as Xehanort freezes him inside his armor from using darkness. Xehanort throws Ventus off the cliff and Aqua rushes forward and catches Ventus before he shatters on the ground.
"Ven, are you okay?" Aqua asks.
"Where'd that little light go?" Vanitas asks and Aqua gasps as she looks over. Willow's heart floats down and reenters Ventus's body.
'No... Willow...' Ventus's thoughts say.
'I made my own promise! I'll remain by your side, Ventus! No matter what! Do not cast me out again!' Willow's voice yells as tears stream down her cheeks in her ghost form as well as her actual body. Xehanort uses darkness on the sky and a blue heart appears in the sky.
"Why don't you leave the little popsicle with me. I'd be happy to look after him and the little girl's body." A guy says and Aqua looks over in shock. She'd managed to drag Ventus's body over to where Willow's was. Both of them laid beside one another.
"So... you can go have your little fight with Terra. You can't be too happy about him deep-sixing your Master." The guy says and laughs.
"Who are you?" Aqua asks.
"You think you three have got some grand role to play. As if. You're only here so that when I finish you off... Terra will succumb to the darkness. So, who wants to go first?" The guy asks.
"Shut up!" Ventus manages to say.
"Oh, so this kiddo thinks he's a full-fledged Keyblade wielder? He's got the angry look down." The guy mutters.
"Go ahead if you want to waste your time." Aqua exclaims, "Keep trying to drive us apart with your mind games. It'll never work!" She sets Ventus down and he struggles to move.
"Terra will prove to you he's stronger!" Aqua yells and she fights the guy.
[Meanwhile]
Terra makes it back to the top to face Xehanort and possibly Vanitas. Xehanort watches as Terra lands in front of them. He beamed an impressed smile.
"Admirably done. I knew this was a journey you could make - over the unseen wall that divides darkness and light. And I was not wrong, Terra!" Xehanort states.
"I have two questions for you, what did you do to Scarlet? How did you turn her to darkness?" Terra asks.
"I did nothing." Xehanort explains, "I was intending to put her in a curse like Willow. But she cast her heart from her body at the last moment."
"Where did she go?!" Terra asks.
"Isn't it obvious? The last bit of light inside you. It's Scarlet's light. Her connection to the Princess of Dreams. Her love for her mother and her knight of light, you combined together." Xehanort explains, "Scarlet is special, you know. She wasn't found by Juniper like she was led to believe. She was born. That's why Juniper and Scarlet looked so similar. Juniper believed that her power would transfer from mother to daughter as it had with her mother before her. But that didn't happen. Juniper's heart and powers went to another, leaving Scarlet an empty shell, easily corrupted by darkness. But her heart was too strong, she escaped her body, leaving behind an empty shell of darkness. Now even her body has been destroyed." Terra holds back his tears. He didn't believe that. He didn't want to believe that. He'd find a way to bring Scarlet's body back from the darkness one day.
'Keep protecting me, Scarlet. Don't ever leave my heart.' Terra's thoughts tell Scarlet even though she didn't respond.
"My friend Ven - you tell me, Xehanort, what did you do to him?!" Terra demands.
"Why, I did him a favor and freed the darkness inside him as well. Alas, poor Ventus never had the fortitude for such strenuous trials." Xehanort explains.
"Xehanort!" Terra yells, getting angry. He and Xehanort clash. After a while, Xehanort fends Terra off and looks at Vanitas.
"Go take what Ventus owes you. And take Willow and Aqua's life." Xehanort orders. Vanitas nods and takes off. Terra gives chase but Xehanort stops him.
"You see how powerless you are to save them?!" Xehanort asks, "Savor that rage and despair. Let it empower you!" Terra thought about it.
"You will pay, Xehanort." Terra declares before fully giving into the darkness, "Was my Master - no my father, Eraqus not enough for you?! LEAVE MY FRIENDS ALONE!"
"Yes, boy, that's it! More!" Xehanort cheers in a sick way, "Let your whole heart blacken with anger!" Terra does. He completely gives into the darkness.
[Meanwhile - Below]
"Aqua!" Ventus says and he struggles to move. Aqua fights off the guy and has a little bit of difficulty. She manages to finish the guy off and he breathes heavily as he wasn't quite dead yet.
"I keep forgetting – don't mess with Keyblade wielders." The guy fires back, "But you know what? That just means I made the right choice." Aqua rushes towards the guy.
"Well... he wanted me to buy time, and I'd say he got it." The guy says and he runs away.
"What?" Aqua asks confused before she gasps, "Ven! Willow!" She turns towards them. Ventus struggles to move. He was so cold that he couldn't move at all. Willow tried to give him extra strength but she couldn't do it.
"Willow! Get into your body!" Ventus pleads.
'It's impossible. Even if I did, I can't wake.' Willow's voice explains, 'It was the deal I made...'
"What?" Ventus asks and he gasps seeing Vanitas jump down towards Aqua, "Aqua!" Willow's eyes widen when Vanitas drops down and attacks Aqua. Aqua falls to the ground from getting sliced. Aqua drops to the ground and Willow's eyes widen.
'Aqua!' Willow's voice says and she uses a piece of herself to create a shield around Aqua which throws Vanitas off. Willow lets out a scream and Ventus's eyes widen. He forces the ice off him and he jumps up and rushes forward and attacks Vanitas in defense of Aqua. Ventus and Vanitas fight and Ventus wins.
"You've done it, Ventus. Now that my body is about to perish... you and I will have to join together. The χ-BLADE will be forged!" Vanitas yells out. Ventus gasps in shock. Ventus gets attacked by Unversed.
"The Unversed come from you?!" Ventus asks.
"It happened when you and I were split in two. The negativity took shape as these monsters. They are what I feel - a horde of fledgling emotions under my control. I released them in all the worlds I could - hoping to lure you away from home and isolate you from your Master and your little light. We needed to make you stronger. The Unversed were the perfect opponents. And better yet, no matter how many times you defeat them... their negativity flows right back into me. You never stood a chance against us, Ventus." Vanitas explains. He steps towards Ventus, trying to merge. Vanitas tries to remerge with Ventus and Willow's scream is heard.
[Inside Ventus]
Willow floats beside Ventus as the two face off against Vanitas who holds the damaged χ-BLADE.
"Willow! Leave!" Ventus demands.
"I won't!" Willow yells and she looks at him, "I made a promise to stand beside you! It's a promise with myself sure, but I won't leave you."
"Willow... when I destroy my heart... I want you to leave. Then your promise will be fulfilled." Ventus says and he rushes forward and attacks Vanitas. Willow watches as tears fill her eyes. Vanitas and Ventus continue to fight and when Vanitas falls, Ventus looks back at Willow.
"Ven!" Willow yells out. He smiles at her as tears fill her eyes. Willow tackles him with a hug.
"Willow... You have to..." Ventus pleads as he looks at her.
"No... Never..." Willow objects, "I hoped to say this in person but... I refuse to leave you because... I love you." Ventus's eyes widen and the two close their eyes as they drift off into the slumber. Their inner bodies vanish in the light as their hearts fly together. They appear hand in hand as they enter the heart of a young boy.
[Meanwhile]
Terra was close to dealing the final blow on Xehanort. Xehanort gasps as the light from the χ-BLADE is shown behind Terra.
"There, you see?!" Xehanort asks and Terra risks turning his back to Xehanort, "The χ-BLADE has been forged!"
"VEN!" Terra yells out in shock.
"And now, Terra, it is time for the final union." Xehanort explains and plunges his keyblade into his chest.
"What?" Terra asks.
"At least our final moment was here. Out with the old and brittle vessel, and in with a younger, stronger new one!" Xehanort explains. Terra stares in shock watching Xehanort's heart float up.
"I swore I would survive... and be there to see what awaited beyond the Keyblade War! And now it is your darkness that shall be the ark that sustains me!" Xehanort yells and thrusts his heart into Terra. Terra tries to defend himself but he's taken over. Terranort removes Terra's armor.
"This heart belongs again to darkness. All worlds begin in darkness, and all so end. The heart is no different. Darkness sprouts within it - it grows, consumes it. Such is its nature. In the end, every heart returns to the darkness whence it came." Terranort explains. He goes to walk away before he's suddenly frozen by the strength of Terra's mind which was fueled by the real Scarlet. Scarlet and Terra appear behind him. Terra wore his armor once more.
"Your body submits, your heart succumbs - so why does your mind resist?!" Terranort asks.
"As long as I am protecting him, he will never submit." Scarlet explains.
"Then so be it. I'll destroy you." Terranort replies. Terra begins attacking Terranort. Scarlet threw out attacks defending Terra the best she could.
[Meanwhile]
Aqua comes to and her eyes widen in shock to find Mickey beside her. She slowly sits up as Mickey tells her that he's glad she's okay.
"Ven! Willow!" Aqua screams out and she gets up. She finds Willow's body laying alone while Ventus stands not far away. Aqua rushes over to Ventus.
"Ventus, are you okay?" Aqua asks and she gasps when Vanitas goes to use the χ-BLADE to attack her. Mickey uses his own keyblade to stop the attack.
"That's not Ven!" Mickey exclaims.
"Correct. I am not Ventus." Vanitas responds, "His heart has become part of mine now. This χ-BLADE will open a door - one that leads to all worlds! Then, keyblade-bearing warriors will flock here from each and everyone one of them, to battle for the light within Kingdom Hearts! And just like the legend says, the Keyblade War will begin!"
"Shut up! I'm sick of your nonsense!" Aqua yells out, "Give Ven his heart back!" Mickey and Aqua fight Vanitas off. Vanitas uses the χ-BLADE and sends Mickey and Aqua flying.
"What's wrong? Giving up already?" Vanitas asks.
"Terra... Scarlet... Willow... Ven... Lend me your strength." Aqua says as she looks at her charm. Her eyes widen when the charm resonates and her Keyblade changes.
"You're just wasting your energy." Vanitas says as Aqua rushes towards him. Their blades collide and Aqua shatters the χ-BLADE.
"WHAT?!" Vanitas yells before Vanitas is thrown back. Aqua grabs Willow and rushes towards Ventus who returns to himself. She struggles to get to Ventus as the χ-BLADE goes haywire. Aqua jumps after Ventus as she holds onto Willow and the three are sent hurtling into the highway.
[Meanwhile]
Terra and Terranort battle and afterwards, Terra drops to his knees. He looks towards Scarlet as the power of the χ-BLADE self-destructing sends Terranort flying. Terra holds onto his key to keep himself planted.
'Aqua, Ven, Willow, Scarlet... One day I will set this right.' Terra's last thoughts say before everything went black for him.
'And I will defend your heart until you are able to set this right.' Scarlet's voice calls out in the darkness.