I'm beginning to feel ashamed about my inability to distinguish the characters these cosplayers are role playing as…
Unless this is Megurine Luka from Vocaloid 2 wearing a red dress, then your guess is as good as mine. Please leave comments and hopefully, we’ll figure this out too!
Thanks again to Yula for the contribution!
EDIT: Thanks to anon and Afiqah for letting me know this is Another Blood from Demonbane!