In a post-apocalyptic world ravaged by earthquakes, grotesque monsters and powerful demons run rampant through the streets of New Tokyo. Only a select few people have been trained in the techniques necessary to defeat these creatures. Brothers Kakugo and Harara Hagakure not only possess the skills, they also harbor the power of the Zero Armor containing the souls of thousands of warriors. Separated from his brother, Kakugo roams the land fighting in order to restore some sort of peace and safety to mankind. However, he finds these monstrosities to be merely pawns to a much larger adversary from his past, who may prove to be his most dangerous opponent of all.
Both anime have a "suit of armor" that takes over whoever wears it. Depending on how willed the person is they can control it or be controlled by the suit. Crazy action, violence, and weird characters a plenty. Both take place in worlds where mankind isn't doing so well and struggling to survive. If you liked one i highly suggest you check out the other.