User blog comment:Viperys/Konosuba Crack Theory (careful, spoilers)/@comment-29694966-20161120120702

There is another background story theory, but involving Wolbach and Demon King.

Komekko's favorite fairy tale story is about a soloist Hero with cheat item. He defeated the Demon King of his time, but then decided to become the next Demon King himself. My theory is that the current Demon King is:

- The hero from the picture book.

- His name is Satou, possibly even related to Kazuma Satou, and

- His powerful cheat "item" is also a Goddess, by the name Wolbach.

- So, Wolbach joined Demon Army, along with the former hero.

The theory would certainly explain the subtle hints throughout the series (e.g. Demon King is very old now and has some close connection to Wolbach) and the cryptic messages from Wolbach (she is sensitive to the name Satou; she also thinks that Demon King will reveal everything to Kazuma when they eventually meet). It's also the most reasonable explanation on why Wolbach would even join the Demon Army and why Axis cultists are allowed to completely purge records of Goddess Wolbach's name.

However, the theory can't explain why the hero is a soloist, if Wolbach is his divine item and companion. So, for the fairy tale hero connection to hold, we'll need information explaining the inconsistency later. It could be stupid reasons like Legends are not always 100% accurate, or that Wolbach was casting her spells from very far away and never demanded share of rewards.

Obviously, we have not even seen the Demon King yet. So everything is just speculation at the momment. It would be interesting to see how much of the theory come truth though, and when we will finally see the Demon King.