User blog comment:B214/Volume 23 discussion blog/@comment-31764731-20170818183934/@comment-29963364-20170822215517

That's why I consider & call them an "Artificiall Sub-Species."

When they reincarnate, they do become "Devils." But since their souls/spirits were originally different races/species, they keep their original abilities, and their physical bodies stay the same (internally & externally), with some changes (wings).

Another thing that differentiates the Pure Devils from the Reincarnated Devils, is that the former naturally have Demonic Power, while the former get it from their Evil Piece(s). Any Devil-based powers they get are added on top of whatever powers/abilities they originally had.

 Tannin 

* Former: Dragon

* Current: Devil with Dragon abilities & anatomy (he's basically a "Dragonoid Devil")

 Akeno Himejima 

* Former: Nefilim (Human/Fallen-Angel Hybrid)

* Current: Devil with Fallen-Angel abilities & anatomy (F-A Wings, Holy Power)

 Koneko (Shirone) Toujou 

* Former: Nekoshou

* Current: Devil with Nekoshou abilities & anatomy (Cat Ears & Tail, Youjutsu) I'm not including Senjutsu, because that can be learned by anybody.

 Zenovia Quarta 

* Former: Human (born with Light Attribute)

* Current: Devil with human anatomy and Light Attribute (allows her to wield Holy Swords)

 Issei Hyoudou 

Former (1st): Human (Boosted Gear wielder)

Former (2nd): Humanoid Dragon (Ophis made his body to be identical to a human body)

Current: Devil with Dragon abilities (he's a Human-shaped version of Tannin, plus he can Dragonify himself like Devils from the Bune Clan).