Amy was thrown into an asylum on her 18th birthday, because she 'accidentally' killed the younger brother. Eventually she started writing Down her thoughts in a small book she found, and things in there show how her mind works.
Echo was having a typical day at school when the unexpected happened a demon appeared. It murdered everyone in her class wounding her fatally across the abdomen . It disappeared leaving her behind in a pool of her own blood . What she didn't know is when you are attacked by a demon and live they pass on majority of their powers. Nine months later she realizes this and decides to exact revenge meeting many people along the way.