This Ridiculous Business of Me Becoming the Demon King in the Future

According to historical records, the Destined Warrior, Messiah Kaslana, will become the Devil King of Reason a hundred years from now, reigning over the whole world and commanding all creation. To obtain the Devil King's power, he set out on a journey across various worlds.

Rejoice, for the true king is about to be born!

(The above blurb is just for show. I couldn't think of anything better, and it has little to do with the story, title included.)