User blog comment:Crimson and Darkness/Shin DxD 3 discussion/@comment-176.54.22.178-20200130133402/@comment-10330822-20200131043554

The Dragon God aura thing was also sneeked into the story to imply that Issei's body is either adapting to the DxD form or is becoming more like it. The translation is kind of dodgy on that.

Still, "Satan" which means, Devil Dragon King is a fair enough title for him. And, if you follow Sirzechs' wish, calling him the Crimson Devil Dragon King, would be in line with calling him Crimson Satan, which is the nickname Sirzechs wants him to have.

I also though the idea of calling him True Devil Dragon God Emperor/True Diabolos Dragon God Emperor was pretty well suited. As he has the power of a Dragon God, the flesh of a True Dragon, and is a devil.