Kouhei works for a cleanup company. One day, when he cleans an apartment room, he finds a notebook. He opens it and it says, "This magic word changes any girls into nymphos." He puts the notebook into his pocket.... The next morning, he whispers the magic word into Yumi's ear, his sister-in-law. She gets sexually aroused soon and presses herself against him. He now gets the magic word....

[From ErogeShop]