User blog comment:B214/High School DxD Hero Discussion/@comment-103.7.39.18-20180627002849/@comment-29963364-20180627040032

I think the whole Divine Dividing-like Wings are a reference to 2 things that were very clearly shown and stated in the series (both Anime and LN):

1.) Issei inserted a [Divine Dividing] gem into his [Boosted Gear].

2.) A previous [Divine Dividing] possessor helped Issei unlock Cardinal Crimson Promotion.

So of course the wings are gonna take some inspiration from the Divine Dividing.

As for the CxC armor looking like DxD armor, the only written description we get of DxD is that it's a slightly more intricate version of CxC, plus black coloring mixed in. Also, we actually see the CxC in vol.23 of the LN (Issei vs Dulio Rating Game). The armor just looks like a "lesser version" of DxD. Hell, fans even mistook it for the DxD armor when it was leaked.