In Dwarfs Woodland/Go through the Mirror (Aqua, Brian and Stewie's Story)

Brian, Stewie and Aqua arrived in Dwarfs Woodland

Brian:

Aqua: Another World that was lost to the Darkness.

They saw a Coffin

Aqua: Is that?

They went to see it and they saw a Boy

Brian:

Aqua: Ven!

Then he disappeared, Brian and Stewie knows that Roxas is inside of Sora and Aqua knows that Ven was still asleep in the Chamber of Waking