Though this seems like a "i love my sister so much" type of mushy shoujo manga, it is actually dark and sinister. The protagonist in trying to live the life of her sister is thrown into a strange classroom with creepy classmates that are all too perfect. She has no one she can trust or rely on, even the ones that seem trustworthy might turn out to be her worst enemy. So far it feels like a horror movie... I cant comment on the romance yet but in terms of mystery i will say that this is recommended