When the peace that once was is interrupted by attacking demons, who kill and rape the people, holy knight Ruvyrias swears to take revenge and restore peace to her world. Thus, she sets out all by herself to defeat the demon king. Despite being initially defeated, however, the demon king does not give up - on the contrary, his sexual desire and greed for more increase. Tia, Lifria and even his little sister Iris as his sex slaves are now no longer enough to sate his lust, and so he devises a nefarious plan to win Ruvyria as a new “toy” when they meet again. Ultimately he succeeds, and now she finds herself defenceless and exposed to his perverse urges…

Keisuke Takatou wakes up in a featureless white room, unaware of how and when he arrived. While exploring his whereabouts, he notices six familiar girls huddled around a large monitor—his childhood friend Kanae Hokari, the class president Miyakou Ando, his English teacher Natsuki Aoi, his junior Rika Makiba, and his classmates Rinne Byakuya and Nemu Manaka.

As they attempt to make sense of their current situation, a voice suddenly declares through the monitor, "The game will now begin." The rules of the game are simple yet brutal; assigned as the "unlocker," Keisuke must select one of the girls as his "keyhole" and violate her in a specific manner. Only after he does this for five rounds will the group be promised freedom to the outside world.

"Withdrawal from the game will result in death," announces the mysterious voice...