Suikyo no Shizuku - Seiin Shimai (The reflection in the water - Horny sisters)

An early work by the studio Double Soft Cream. The main character of the 3D hentai is not young and was once a very successful teacher. Now he no longer works and simply wastes his life. However, on one of the ordinary unremarkable days, he receives a mysterious letter from his former students asking for help. He hurriedly packed and left for the specified address. Upon arrival, he discovered a huge mansion, on the threshold of which one of the students was waiting for him. Soon he receives an unusual artifact from the girl's hands, due to the influence of which he soon begins to lose consciousness. Waking up, he realizes that he must unravel some terrible secret of this mansion...