Kingdom Hearts 3D: Dream Drop Distance The Novel

"Sora, Riku, I would like the two of you to take the Mark of Master Exam." Their journey to bring peace to the world just barely over, Sora and Riku have received news from Yen Sid regarding a new threat drawing near. In order to face this new world crisis, Sora and Riku must face the Mark of Mastery Exam. For this the must go to the "Realm of Sleep," release the seven Keyholes of Sleep, and gain a new power.

(Source: Gold-Panner)