The Book of Five Rings
Part of this process was a plot by which Satan managed to trap Mym in Hell. Mym eventually led a revolution of the lost souls and secured an escape route, employing lessons from Miyamoto Musashi's famous treatise, "The Book of Five Rings", to defeat Satan in a one-on-one battle. However, during his absence, Satan has manipulated the geopolitical situation such that international tensions everywhere are at an all-time high, and the world is on the brink of apocalypse.