Especially because it's actually difficult to expect a dark series from a Cute Girl+mecha combo (like it was for Madoka's Mahou Shoujo reconstruction), no one might actually see it coming so it's gonna work (unless the otaku are on their guards) ... what's left is having the staff saying :
"it's gonna be cute & moe, sweet & fluffy from the beginning to the end" and it'll be the perfect trolling
