In a post-apocalyptic future, Abel Nightroad does occasional dangerous work for the Vatican, to whom he is extremely loyal. While the apocalyptic war has long been over, humanity is still entrenched in a shadow war against the vampires. Lady Catherine, the leader of his operations group "AX," seeks to prevent a renewed full-scale conflict, but there are many forces on both sides bent towards war. As Abel and the rest of AX try to stop this, he encounters a young girl who will be the key to humanity's survival or demise. Now, Abel must not only fight for humanity, but also try to face his regrettable past...