User blog comment:Lex wa Kaiho/What is Lumen Histoire?/@comment-26399354-20130627162312/@comment-4829046-20130627163925

You can reach any world in any media via portals, assuming of course, your body can survive the adverse effects of being warped. I like series where passing through or opening portals to other dimensions results in serious drawbacks. One of the reasons why I love 'His Dark Materials' by Philip Pullman.

Though it is accepted that short-warping and sliding between dimensions are a lot less dangerous than actual warping. The anima follows the sliding concept not the more complex dimensional travel. Here is how it works

Parallel Dimension = short-warping, sliding

Completely separate universe = proper space travel with portals and calculations and most of the time resulting in completely different physical appearances due to passing through to a different reality.

And I don't think Jellal would be in this OVA.