People, this is gore-y and involves children in that gore. Take care and skip this one if you are sensitive to the topic! (Also involves a creep that's interested in childlike heroine because she's untouched, felt a bit pedophily to me, even if it's not necessarily pedophilia)
Edit: Also, we've got really nasty child abuse in the later chapters. If you don't like reading that, you might want to skip this one.
@yatsuki
To be fair, if you would just gas all the kids - sounds brutal, but if they can awaken, they need to die before they realize it, and poison is riskier - there wouldn't be a story.
Also, based on the oneshot, they are possibly harvesting something from the kids - wouldn't make sense to have so many of them otherwise. If what they need is damaged by poison or drugs, it makes more sense to just kill them the traditional way.
God this sounds morbid xD but hey, this is a pretty brutal horror manga! I really liked the oneshot btw.