Ehh... Isn't that random and sudden... Somehow and for some reason, shadows appear and suddenly start sucking people's souls up. (Eh?)
Anyways, can't judge this ending development until I see how the anime ends everything, but I hope they don't end up creating a new setting or character just to finish up the story.
Anyways, poor Muscle-megane and every other character that never got a background story...
