User blog comment:B214/Volume 22 spoilers/@comment-175.110.173.31-20160829100254/@comment-9595671-20160829111633

Yeah, I heard Ishibumi's seen enough DxD doujins he could use some of the ideas in the story if he wanted, he did name one of Xenovia's attacks after a fanfic about Xenovia and Irina that he approved.

The reason he can't is cause of his... publisher I think?