You develop Erectile dysfunction from the stress of working at a black company. Not even visiting your favorite prostitute can cure it. She tells you that she heard that there is a hidden hot spring called "Seikon no Yu" that restores sexual desire deep in the mountains.
You decide to go there but the weather suddenly changes and you find yourself in danger. It is by chance that you find yourself in front of a western style manor. You head towards it and are welcomed by the maid.
Courtesy of the Chichigami family, you are welcomed to stay the night. Manami, wife of Jinnosuke the head of the household, approaches you with an offer.
"For one week, I would like you to be the night time tutor for my two daughters and teach them how to attend to someone at night."