Based on the game by Front Wing.

When the summer break began, Jinno Naoto and Manabe Rika confessed their thought they had since their childhood and began to go out with each other. Suddenly a boy named Asmodeus appeared. He said he was a devil, and he tried to take Rika away. Naoto did his best to save Rika from Asmodeus, but he couldn't anything to do with devil's power. At that very moment, a girl Luvriel, who name herself an angel, came and saved them.

They took Luvriel injured in the battle against the devil. There, Luvriel told them the surprising things; angles in Heaven and devils in Hell have been fighting for a long time, and the devil would attack them again.