Based on the erotic doujin game by Tsukinomizu Project (月の水企画).

Lu Luu had went missing after heading to the town castle and Eliza and the gang went out to look for her.
There they found a girl named Jard bound up and violated...
To their horror, they discovered that the Acklem knights capture female adventurers and offer them to monsters as human seed beds... and they were next...