Demonizer Zilch

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 himself 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.