Minase Youmu to Hontou wa Kowai Cthulhu Shinwa

One day, an ordinary high-school girl named Minase Youmu is kidnapped up in the mountains. Her kidnappers claim that she has taken some kind of "medicine" and that there's no going back. Luckily, though, a former detective named Sanpouji Kotetsu happens to pass by where she is being held, and rescue