1400 years ago: first murderer demons get spotted.
700 years ago: western technology start to get used for rebellion.
500 years ago: murderer demons learn to acquire human appearance in Transylvania.
18 years ago: a huge massacre takes part in Japan.
10 years ago: a murderer demon awakens at the age of six in Japan.
Nowadays:
Sakurano Mana gets worried by the murderous desire overflowing her body.
Onose Kiri is troubled about her past when she lost one hand and one leg.
Kaiho Kazuki investigates murderer demon he killed at the age of six. Then Kazuki meets these girls and other strong people in this town full of death scent.

[Edited from vndbreview]