Haruki no Saidai no Teki wa Risei.

The girl he's in love with is coming over to his place, alone. Tagokoro Haruki decides on Saturday to prepare for this situation. Haruki is a virgin, as his raging boner in the morning can prove, and his step-sister — Tagokoro Anne — plots to fool around with his fluttering heart. This leads to him skipping his Saturday shift... During lunch time, his remarried step-mother — Tagokoro Madoka — plans on seducing him as a way to satisfy the itching inside her. She decides on doing that on that Saturday, when her husband is out of the house. Haruki's biggest struggle is to stay rational: to beast or not to beast? His Saturday had just begun.