Ok, following the theory somewhere that these stories Yuuma told has relations to what he's actually experiencing, this Perfect Copy story may imply that the Hina who is suddenly back this chapter may not be the Hina we've known so far, perhaps just a random soul who strongly believes "it" is Hina and "inherits" her memories.... or it could be "Yuuma's mother" now believing she's Hina so Yuuma will let down his guard