This reminds me of a scene in a JAV movie I saw years ago.
Simple plot set up, group of school girls staying at some inn who are molested in their sleep by the all male inn staff. Ultimately ending in an orgy in the last scene.
In one of the sleeping scenes the guy turned over the girl and proceeded to grope her ass. It was then I noticed that her ass was really tiny compared to his hands. I was actually worried she may have been a minor.
I found out much later on the actress' name is Saotome Yui who seems to be a rather petite girl even by Japanese standards but is very much of legal age. With the added combination of make up and costume making her look even younger she has starred in numerous fake loli movies.