Daiamondo wa kizutsukanai (1982)

This one’s got an Asian teen girl with long, straight black hair and a slim build getting intimate with a guy in a bathroom setting. He’s got short, wet black hair and a muscular build. They seem to be in a bathroom, possibly after a shower. The girl’s got a petite frame, but she’s getting fucked hard. The camera’s got a medium shot, mostly frontal. The setting’s pretty standard, bathtub and toiletries in the background. The girl’s reactions aren’t super enthusiastic, but she’s definitely into it. The guy’s doing most of the work here, fucking her from behind.