Demon Lord Wants To Escape

In the year 6338 of the Continental Calendar, the release of an autobiography caused an uproar.
The first sentence on the book is. "Facing the shy tentacles of my fiancee who is like a female insect, and looking at the ability of inhuman favorability of the opposite sex max, I know that I must escape from this marriage! But what I don't know is that... is just the beginning."
However, no one knows that the author of the autobiography is actually the demon lord who unified the world two thousand years ago!