Brief scene of a nude couple having sex; breasts are visible but no explicit detail is shown.

A man walks in on a couple having sex. The shot is from behind and you see a woman's bare back and buttocks for a brief moment before they run out of the room.

Couple seen having sex only butts are shown.

Around 18:28, when he goes down the stairs to go to Room 12 - the couple is having sex. She is naked on the guy and both of their butts can be seen and some side boob. It only lasts a few seconds.