On that day, a single adventurer met the end of his life. Under a clear sky, struck by lightning. And then, the young man Alto descends upon the land of Purgatory.

What he first encountered in Purgatory, the world of demons, was... a lonely Demon Lord who had awakened from a thousand-year slumber!?

The Purgatory life of the Demon Lord and the two of them begins in hard mode. Their enemies are all the demons in Purgatory. Meanwhile, they don't even have a place to live. However, Alto had a trump card. It was a secret art passed down through his clan to create a "Demon Tower." If they made this their base, a minimal life would be—

Huh!? This Demon Tower is going to go beyond the ground and even reach the heavens!? How many floors will that be! Don't say such absurd things!

Such an absurd story now begins!