Near the start of the game, Mistress has the protagonist Sugita Yushin and Jinmuji Miyu, a girl from his class, kidnapped and taken to a dark and dank dungeon. To their surprise, they each have strange metal collars around their necks, but are otherwise unrestrained and unharmed. Shortly after the two awaken, Mistress appears on a monitor in the room and explains that she plans to have the two abducted individuals participate in a little experiment that she has created. To prove she is serious, she has her maid, Shuri, press a button, which immediately causes the collars to give the boy and girl a painful electric shock.
Mistress's instructions are simple. Each room of a dungeon is a puzzle, and the two must work together to discover an exit. If they fail to do this within the time limit that she has set, the doors will lock permanently and they will be trapped inside until they die. Each of the solutions have been carefully crafted to create humiliating ordeals for Junmuji. She is forced to urinate on a door unlocking mechanism, recite a very detailed and sexually vulgar demand at the top of her lungs, and then crawl through a pipe first, providing Sugita an up-close view of her panties. As they exit the pipe, Mistress delightfully informs them that a combustible chemical had been lined along the inner wall of that pipe, and that they must quickly take off their clothes before their bodies catch fire.
The perverted solutions to the traps continue until the two finally arrive inside of a room with a bed. As the final test, Mistress says that they must have sexual intercourse to earn their freedom. Junmuji is disgusted by the very thought of it and refuses. Hearing this, Mistress suggests that Sugita do so by force, but he also refuses. The monitor shuts off, and knockout gas immediately begins to fill the room.When Sugita reawakens, Mistress appears before him, but Junmuji is nowhere to be found. Shuri reveals that the girl has been taken to a different room, where she is being sexually tormented. Mistress reminds him of how Junmuji rejected him so harshly, and commands Shuri to service him orally. The villainess then states that there is still a chance for the two of them go go free, as long as he does exactly what she asks of him. Sugita accepts.
Mistress has the protagonist rape Junmuji, and then several other girls who he is acquainted with soon after. Eventually, he is given the opportunity to escape with one of them on the condition that he forgets everything that transpired here, as if it were all just a dream, and most importantly, that he never reveals it to others.Sugita escapes with a female captive, but refuses the parting request of the Mistress: In this ending, Mistress and Shuri recapture Sugita and restrain him in a room from which he will not be able to leave until he as ejaculated 10,000 times. Days pass and Mistress manages to get him down to 9,917 left to go, and then leaves. Unable to control herself, Shuri forces him to climax on her own, stating that she won't tell the Mistress and that it will be their little secret. Sugita is shocked to see that the count did not decrease this time. Mistress returns and resumes her fun, but when the number reaches 9,866, the couter screen suddenly goes dark. Feeling that there must be a glitch in the system, Shuri unplugs it for just a moment. When it comes back on, Sugita is horrified to find that the number has been reset to 99,999!
"Was that the number it was before?? My memory is a little hazy..." Mistress says.
"Yes Mistress, there is no mistake that that was the number," adds Shuri.
And thus, Sugita realizes that he is only at the very beginning of his nightmare.
Sugita escapes with a female captive, but sticks to his word: Sugita remains faithful to the girl. The two live happily ever after and Mistress is not heard from again.
If Sugita is reluctant to leave, and continues voluntarily ravaging the girls, another opportunity is offered to him.Sugita accepts an offer to work alongside of the Mistress: Shuri transfers ownership of the shock collar remote control over Sugita, and Mistress grants him the right to abuse the five now-pregnant female abductees in whatever manner he sees fit. Sugita remarks that the villainess's smile is still as cruel as ever, but is relived that it is no longer so towards himself. A happy ending for the darkly corrupted Sugita, he remains and spends the rest of his days with his new harem.
Sugita accepts an offer to work alongside of the Mistress, but decides that he'd rather have her instead: This is the only ending where Mistress gets close to some sort of comeuppance. Sugita and Shuri conspire together to drug Mistress so that she can be his. Of course, because Mistress is already a master of perversion, she doesn't mind and instead fully embraces his desire.