In the ancient greece period, Yuu is seen in his Seaph form as an angel with six white feathered wings, but in modern time, Yuu has a giant black wing. Is this due to Asuramaru changing him? Or is The King of Salt trumpet seraph different from Yuu's old seraph form???
Between the flashbacks, and what we are shown with Yu in the present, it is one tough guessing game! The giant black wing one seems to be an out of control, kind of intermediate stage. Perhaps the complete seraph is the multiple winged one, maybe Yu now has the genes for The King Of Salt seraph, or something else!
It's a bit more different than that, Yuu's black wing is his wings, the only reason they're like that is because yes you were right because of Asuramaru. Asu is repressing the angel's full power so that Yuu doesn't get fully controlled by the angel or else he wouldn't be able to get control of himself back..
They're the same 'form' just one is incomplete and the other is complete, his incomplete form is the more 'messy' one, with Yuu's clothes being torn and such.
Sorry if this doesn't make sense it's 1 am and I'm tired
Asuramaru is stopping the angels full power to stop Yuu from never being able to get control back
Demon powers interfering with a seraphs, quite handy! It might be a wait and see thing, but if Yu appears in a seraph form without Asuramaru's powers, and if he had four wings or something, it may mean the present Yu with the King of Salt is a different seraph to the one of the past. Seeing that would be helpful in knowing whether Yu is linked to the past one through a spirit/time transfer, or if he can be biologically altered with different seraphs able to be added.
Well no, according to Kagami sensei's interview on 2015 he directly himself said that Yuu doesn't have those kind of wings as his demon Asuramaro doesn't let him to complete his transform if you want I can give you that picture and it is also available on ons official site too