Cain, a wandering adventurer, is walking down a road toward town when suddenly, everything goes dark. He’s stuffed into a bag and kidnapped.
When he’s let out, he finds himself face-to-face with a young dragon girl. She’s the princess of a nearby dragon castle, who snuck out to visit the human world for fun. However, after being scolded by the castle maid who came looking for her, she’s too embarrassed to return on her own.
The princess begs Cain to accompany her back to the castle and help her apologize to the maid. Seeing an opportunity, Cain agrees—but his real goal is to have his way with the dragon princess first.
And so begins the merciless “punishment” of the monster girls.

[Translated from dlsite]