One rainy day, Nakanishi Mina is abruptly kidnapped.
When she wakes up, she's handcuffed to a bed in a mansion.

In comes the butler, Shirayama Masaya, to explain that she had been abducted under the orders of the mansion's owner.

The owner, Iwatsuki Kanata, hides his face with a mask.
He keeps Mina handcuffed and rapes her, night after night...

[Translated from DLsite]