From Yen On:
With the Door to Darkness closed and the Organization defeated, all is right with the world. Everyone has gone home, and the adventure seems to be over. Until Jiminy discovers a cryptic message in his journal: “Their hurting will be mended when you return to end it.” Jiminy knows he didn’t write it, so where did it come from? And what does it mean? To discover the truth, King Mickey and his pals at Disney Castle decide to turn the journal into a digital datascape but they’ll need the help of someone on the inside. Fortunately, another Sora within the data is ready to lend a hand and get to the bottom of the mystery.

Based on the spin-off video game, Kingdom Hearts Re:coded.