Nudist Beach ni Shuugaku Ryokou de!! The Animation

Tomboy or gyaru, by two-piece swimsuit or by scholar swimsuit, doesn't matter, there's two characters in each of these hentai with tanlines, that's all you need to know, well there's also sun beaches in both of these and there's only one guy involved in the sex scenes making them both harem, so there's that too, and furthermore, there's a girl with very young looks in both. Ok, now that's all. 

Both are hentai featuring at least one girl in each with exquisite tanlines, one is tomboy, the other one is gyuaru, but whatever, Bokura no sex adapts three short stories from the manga of the same name, so only the first one with the short haired beauty is similar, but who cares? Those tanlines are to kill for, there's also a summer theme in both, maybe? Go for the tan, man. 

The beach and summer theme is present in both of them, Resort Boin has a few scenes in the beach, but Nudist Beach has most of the action happening inside a tent, but the beaches and bitches are definitely present, besides that there's a girl with tanlines in both of them, Resort Boin case is tomboy oriented, while Nudist Beach is a more gyaru type of girl, but tanline is tanline, plus there's only one guy giving in both.