I haven't finished the manga so I'm not sure if it states anything about this, but I've always been curious about this. What does it take to turn on Seraph mode? Are vampires able to do it? Out of Kimizuki, (Mirai is of course transformed but we're not exactly sure how since it looked quite different from transforming Yuu) Yoichi, Yuu, and Mika, we've only seen Yuu transform and stuff. What does Krul want from Mika's Seraph gene anyway? Does she want to use it somehow, or does she know that if Mika turns into a vampire he won't be able to transform? I'm just confused how all this Seraph transforming works
I cant answer for sure but I'd assume yes since Shikama looks like a Seraph while being a demon, and demons are starved vampires? So i think vampirism wouldnt make turning into a seraph impossible, after all Shikama made Krul, Ashera, etc a vampire in order for them to become "Michaela" ? Or at least these things seem to be connected somehow.
For Krul and Mika... I'm might add some thoughts later when I have more time ^^'
Shikama Doji has his own rulebook for vampire, demon and seraph related areas. For turning into a seraph, something chemical seems to be required for the seraph transformation - something in Yu's cursed gear supplements, the injections for Mirai.
Not sure what Krul was expecting for Mika's seraph form, what with him being a vampire. Seems to be another will have to wait and see thing.