Both Ah J and Satan are mathematic geniuses, but Ah J uses his talent to save people, while Satan to kill. They have been battling against each other with the Equation of Life and the Equation of Chance in their hands. J fell into a coma in order to stop Satan from massacring, which means that nobody is able to hold Satan back anymore. Satan uses the super AI computer Angel to get the Cloud Database of the global population from the company, Ant. With his Equation of Chance, Satan becomes the death sickle again. But this is all anticipated by Ah J before he lost consciousness. He left a Lock of Heart to temporarily get in the way of Satan. When Satan was stuck and didn’t know what to do, he met a young man who looks exactly the same as Ah J. Who is he... and if the Lock of Heart can be unlocked soon?