Traveling Through Another World, I Changed from a Brave Man to a Demon King

The first thing to do when traveling to another world is to become the strongest demon slayer and kill the demon king! But why did I become the devil? Still facing a life and death crisis? That won't work! I, the devil king, must defy God's will, seize luck, and become the strongest! This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.