I missed this memo...

[Reijin]

It is actually a sequel.

This.

I'm pretty sure given how drastically it jumps off the path of being one though has left them wanting to make a "true" sequel, as they've mentioned it a number of times. The only thing Cross actually has in common is a SLIGHT "other world" theme, and a few forced in references to previous characters and the events, but the times when these are mentioned seem to really have no purpose for being there other than to attempt to spray superglue in and bind them.