A nice scene. This reminds me one of my own experience. But it was not any sexual activity. Several years ago I had to stay with one of my best friend when I visited the city he was working for a month for an assignment related to my job. As the rents were high in this city his own sister who was studying in the same city was sharing the room with my friend. However, my friend and his sister allowed me to stay in the same room (It is a big one) for this month as my friend trusted me well. Any way I kept his trust. We used the washroom which was located outside the room for changing cloths. Anyway my friend's sister used to wear panties under her night dress as the lady here. As the nightdress was somewhat transparent her panties were visible. Seeing her panties through her nightdress aroused my sexual feelings. But I managed to control myself.