I’m a Hero, but I’m on the Demon King’s Side!

(This is a wholesome, one-on-one romance with a slow overall pace. Basically, it's about a wicked Demon King training a clueless protagonist~)

Yu Xi: “Your Majesty, this is the 168th formation the Church has used to summon heroes. If we destroy it, they won't be able to summon any for a while!”

Demon King: “...”

Yu Xi: “Your Majesty, I know a secret passage that leads straight to the Pope's chambers. How about we go over and kill that old geezer?”

Demon King: “...”

Yu Xi: “Your Majesty, why don't we just sacrifice all of humanity? I can handle it!”

Demon King: “I... don't think that's necessary. Aren't you being a little too extreme?”

Yu Xi: “Sacrificing all of humanity outright does sound a bit much. We could first set up a sacrificial formation in the Church's nation to draw the attention of most of humanity's gods. Then we can ambush the gods left alone. How does that sound?”

Demon King: “Here, here. You can be the Demon King!”