Satan's Own Plaything

In a world filled with magic and demonic/angelic beasts that fight for either side. The world was split into two different factions. God or Devil. Obviously, most of the normal humans go to God's path but they are mostly useless as they have no talent in magic. To later expand the topic of these two factions, there are four children that are born with either the mark of the Devil or God. These marks are given to two people each, they will be blessed with immense power. Capable of nearing the actual divine being's own power with enough training. One out of the two mark bearers are actually able to get power that is directly related to the person that their mark involves. Are they the only marks? Who is giving those marks? This story follows Kota, a boy that has been in the Human Realm since his birth. He holds a mark of the devil, showing his importance to Satan. Kota is always bored despite his outer state, this forms less combat performance for him. If someone even manages to get him excited, nobody knows what will happen. In due time, Kota has shown extreme power that is not even comparable to other mark bearers. Is there something special about him?