Fallen Angels, tainted by their own desires, have descended from heaven. Their goal is to corrupt humans by making them give in to their desires. By doing so, the Fallen Angel proceeds to become a Demon. 3 Angels, Lemit, Racquel, and Chiseri have been given the task to hunt down those Fallen Angels. After, being saved from one such Fallen Angel, Kazunari Shijou is pulled into the conflict. His existence has also caught the eye of both Angels and Fallen Angels alike due to a power inside of him. And if left unchecked, his power could corrupt him and lead him to being judged and killed by the Angels. Chiseri and the other Angels take it upon themselves to make sure Shijou's power stays under control in more ways than one. Chiseri has taken a particular liking towards Shijou though. Why is she drawn to him?

Following the untimely passing of his childhood friend and his little sister, Io Haruomi is constantly haunted by their deaths, forever feeling powerless and unable to escape the guilt he feels for letting them die. Despite this, he continues to press forward, attempting to enjoy an ordinary life. He goes to high school, hangs out with his friends, and generally passes off as a normal 2nd-year high school student. One day, however, Haruomi encounters an "Eda", a girl with glowing red eyes and demonic powers. Amidst her escape from the "Seven Great Gospel Organizations", she reveals that he too is an Eda, and the powerlessness he feels is completely unfounded. Before he knows it, Io Haruomi is thrown into the middle of a battle between man and devil. And as his eyes too begin to glow red, the side he is on is no longer so clear.

Sixteen-year-old orphan Yuuto Amakawa has terrible cat allergies. So when he finds himself suddenly face to face with a beautiful girl who makes those allergies act up one morning, he’s left wondering about her identity. And when she saves Yuuto and his friends from a demon spirit with a very real, very sharp sword, she reveals herself as a sworn protector of the Amakawa family and a demon spirit to boot! Poor Yuuto, now that he’s living with an otherworldy samurai catgirl, his runny nose is the least of his worries!