You want nothing more than to relax at your late grandfather's old mountain hut, when you are suddenly surrounded by a thick unnatural fog. To make it worse, dangerous monsters lurk in the woods and make survival difficult. But there is a glimmer of hope. A girl that was able to flee and now lives with you. You forge a pact to help her out in return for special "favors". And that is only the beginning. Your goal: Survive, find out what happened and most importantly, build your own post-apocalyptic harem.