User blog comment:B214/Volume 21 info & spoilers/@comment-142.68.203.184-20160510112615/@comment-27876048-20160510144801

Ishibumi said he wouldn't be expanding the subplot for that part of the overall storyline in the main series. Any potential references or info regarding the other world/dimension has already been explored in the main storyline and in High School DxD EX. If Highschool DxD gets a sequel series or any spin-offs then maybe the plot involving Chichigami and the dimension he comes from may get some attention.