The action of the story takes place in the fantasy world of "Aria". The main character (the girl knight) investigates a complicated case on the mysterious disappearance of women throughout the city. The investigation led her into a terrible cave, where a terrible monster was rumored to live. As usual it happens-the rumors were true, and the main character was trapped by a monster. All the girls were at that hour and found they were all honorable knights of the Kingdom of Aria. Now the Main character and numerous girls are forced to endure the attacks of monsters with tentacles and take their sperm to find a way to escape.