[It’s a familiar dungeon.] Inside a medium-boss room of an RPG game that he played again and again until he can get there with his eyes closed.
Waiting for a hero, a demon who exists only to be defeated, got his former life memory revived.
Knowing that, in his previous life, he was a nothing-special college student-
Continuing to stay as a to-be-defeated mid-boss is a no.
The determined him, decided to defeat the boss and escape the dungeon.
That which was obtained in the process was a doping item called “pearl piece”. (JP: ”珠片”) The demon, who was ordered by the goddess to collect the 15 pearl pieces that was scattered around the world, decided that after all this, he at least want to travel around the world of his favorite RPG game. This would one day become the legend of the Demon God of Oeyama, the demon romance story.