User blog comment:B214/Volume 23 discussion blog/@comment-172.56.17.58-20170417051436/@comment-31137559-20170419133955

Can you properly state where it said that Millicas was the 'rightful' heir? All I heard was that Millicas was next-in-line for heir after Rias, making Rias the main heir and Millicas the second heir.

And Issei isn't just a human anymore. He is a devil. Can you deny that? He's a resident of the Underworld who's going to be Issei Gremory when he marries Rias. Someone like Liban Crocell had one parent that was a devil and the other was a human only. Issei is a dragon AND devil. Halfbloods only apply in the sense where the other species isn't a devil. Oh Issei doesn't have devil blood running through his veins. Yet he is considered a devil. Issei is one of remarkable strength who has basically gone farther than any reincarnated devil before him in so short of a time. He has the rank, status, and strength to be a top figure in the Underworld. Would they really deny his child the right to inherit the house? Again Ex is different because his father is considered a devil in the Underworld despite not being a pureblood devil. If the house was going to go extinct because of that then Zeoticus and Venelana would have stated it. By saying that Ex can't be the heir, that's basically saying Issei has no right to marry Rias. But he got up in status and created a name for himself. That will cause a lot of commotion if they deny Ex the right to heir. Halfblood devils not inheriting the house apply to those species that AREN'T devils. There should be no point in them denyng Issei's son the right to become heir. Or else they would have stopped him from being engaged to Rias.

Issei just used what the pureblood devils value to rise up in rank. And that is strength. And if they were so concerned with the pureblood thing, then they wouldn't have allowed reincarnated devils into their society. Because some have risen up in rank like Tannin and Rudiger Rosenkreutz. Their species is already becoming mixed. And we can say there are more reincarnated devils than high-class pureblood devils. Their society is already becoming mixed. Reincarnated devils are rising up in rank.