The Imposter (1973)

The brunette leads most of this one — long brown hair, slim frame, and an aggressive grind when she’s riding the guy in the office. They start fully clothed, shuffling papers like they’re pretending to work, but she’s already unbuttoning his pants and sinking down on him right there behind the desk. Camera stays wide so you see the whole room, which makes it feel more like a fantasy you stumbled on. Later, it shifts to a bedroom setup where the same brunette is on her back, getting plowed by a different guy this time, deeper strokes, sheets moving with the rhythm. The blonde shows up out of nowhere — long wavy hair, pale skin — and starts going down on her while the guy keeps fucking. They switch at one point: the blonde gets on top, slower, more grinding than bouncing. There’s a fake medical scene too, stethoscope nonsense, guy pretending to examine her on a bed like she’s a patient, but it’s clearly just an excuse to get her naked. Lighting stays dim throughout, mostly pinkish tones, close-ups on faces during orgasms.