Everyone's Loose Screw summary:

Junior high school student Misaki Nanao realizes the people of the town she lives in are slowly going insane. At the same time, she starts seeing Beherin, a mysterious demon. “If you make me believe you, I shall help you”. Misaki believes the demon’s words and talks about her terrifying personal experiences; however she gets dragged into people’s increasing insanity, horrific incidents and a huge conspiracy.