Realm of Darkness
As Sora returned to the gummi ship, Chip and Dale called with distressing news: they’d lost contact with Riku and the King within the Realm of Darkness. Sora let his heart be his guiding key, and went through the gate that he created.
The gate led to the Destiny Islands, where Sora found an old Keyblade lying on the beach. Sora discovered a 
door that could only lead to the Realm of Darkness, and he proceeded through it alone, leaving Donald and Goofy to anxiously await his return.
Sora followed Riku’s voice to the shore of a dark sea. There, he found his friend and the King barely holding their own against Aqua, whose heart had been consumed by darkness. Sora prevailed over Aqua, and pulled her from the sea as she began sinking into its depths. At long last, Master Aqua returned to the realm of light.
Aqua wasted no time in traveling to Castle Oblivion to awaken Ventus. Sora decided to go along. As she arrived at the gates, Aqua raised her Keyblade and unlocked the castle, restoring it to its original form, the Land of Departure.
Inside, Ventus was found asleep on a throne, but Sora and Aqua were not alone; Vanitas had followed them into yet another bid to take control of Ventus by force.
Aqua fought gallantly against Vanitas to protect her brother-in-training and keep the rest out of danger, but her opponent’s underhanded tactics proved too much for her. As Vanitas raised his Keybade to 
deliver the final blow, Sora cried out for help… with all his heart.
There, deep down inside him, he heard the voice of Ventus, who revealed the power of waking had been inside Sora all along.
Sora’s power of waking returned Ventus’s heart to his body, turning the tide of the battle and forcing Vanitas to retreat. Aqua and Ventus rejoiced in each other’s company, the two lost Keyblade wielders reunited at long last.
