Os Imorais (1979)

Starts with a hot outdoor moment — this slim brunette in a light pink top with decent cleavage is sitting on a bench, making out hard with some dude under an umbrella. He’s leaning over her, hands all over, and you can tell they’re both into it. Later, inside what looks like a living room, she’s riding the same guy on the couch while another couple just watches. The brunette’s got that long wavy hair flying around as she bounces, and you get a clear side view of her tits moving. The other girl’s blonde, slim too, and she’s just sitting there with her guy, touching shoulders, like they’re waiting their turn or just enjoying the show. No full-on group action, but the vibe is definitely social and handsy. Lighting’s dim but you can see everything — good angles on the riding part.