Seifuku taiken torio: Watashi uregoro (1981)

Starts with a slim redhead between the legs of a brunette with nipple rings—both look early 20s. The redhead’s got a thigh tat you can see every time she leans in for a lick. They’re on a couch in some dim living room, all warm lighting and shadows, so you get a clear view of the action without any cheesy angles. The brunette’s got her legs spread wide, and the redhead’s really taking her time, switching between slow licks and deep tongue work. Later, the camera catches a dude in his 30s jerking off in the background, but the focus stays on the girls—good call, since the oral’s the best part. No fluff, just solid girl-on-girl with decent chemistry.