Board Thread:Questions and Answers/@comment-90.176.7.225-20140520182401/@comment-75.18.255.142-20140614203713

It is theorized that Yuzuru was drifting between worlds and since he lived a fulfilled life he wasn't meant to go to the afterlife, but he lost his memories during the drift making him enter the afterlife as result. This means that the travel between these two worlds can be different for people.

Another could be that Kanade was never going to leave the afterlife because her reason for staying would be impossible because Yuzuru lived a fulfilled life so some higher force made it so he lost his memories to go to the afterlife to solve this problem.

Lastly which I think is most likely is that this is the supernatural plane of existence. The fundamentals of this world are different from that of their known reality. Things like time, space, and matter may be different in this plane or have no true relevance in the world of the Atferlife.

Similar to what Yuri said in the first episode: Don't try to understand everything, instead accept everything as it is.