[Eleutheria]

More like, Kamui phases stuff to a different dimension (one way).

Tobi phases an area around him back and forth between dimensions - Kakashi sent the Rasengan to a different dimension at the same time Tobi phased there, so when Tobi phased back, the Rasengan was brought back at the same time and hit him.

Problems with this analysis - why didn't the Rasengan dissipate without Naruto holding it? Why didn't the Rasengan hit Tobi in the other dimension?
EDIT: Happened too fast for Rasengan to dissipate completely. And I think the Rasengan did hit Tobi in the other dimension