Kingdom Hearts: Birth by Sleep

Long before Sora was chosen by his Keyblade, the worlds’ safety lay in the hands of Keyblade Masters. Three youths — Terra, Ventus, and Aqua — have been training long and hard under Master Eraqus to prove that they, too, exhibit the Mark of Mastery. But they will soon find themselves in the middle of a crisis affecting worlds far beyond their own—just as another Keyblade Master, Xehanort, goes mysteriously missing. Three friends, three destinies. Everything will link back to the beginning.

(Source: Amazon)