The
game presents two storylines — you will play through the same world with Riku and
Sora but
visit different areas and play different scenarios, as they are both
in parallel worlds of the same universe.
To give a brief summary of the
game's premise, Yen Sid assigns
Sora and Riku with
visiting the Sleeping Worlds and open the seven Sleeping Doors as their Mark of Mastery exam, which they must complete
in order to become Keyblade Masters.