Are you certain nobody steps into your home while you're out? Have you ever noticed small changes, when you come back home at the end of the day? A cushion slightly moved on the sofa, a juice bottle a little less filled up than when you put it in the fridge in the morning, a shampoo bottle you were sure to have closed that you found open? You noticed, then you went on to your business, because after all it's probably your memory playing you tricks, isn't it?
For Youko, it's real. Ordinary at first sight, this 21-year-old girl has vanished to escape from her former life. We don't see her, but she's here, just under our nose: she lives at our homes during our absence, going from one flat to another depending on her needs and whims.
If this new existence is at first carefree and exciting, Youko will soon know better. She thought she's the only one like this, she's going to discover a parallel society where violence is ubiquitous. Clandestines, criminals on the run or mere citizens who turned their back on society for more or less honourable reasons, the leeches are fighting over our homes, calling them nests; they are fighting in bloody wars for territory and lead vendettas that more often than not end up in slaughter.