I found these babies inside a 1960 edition of 『別冊笑いの泉　ユーモア・グラフ』 (Bessatsu warai no izumi, "Fountain of Laffs: Humorgraph(y) (Supplement)"), which bills itself as a publication of "sexy photography and tasteful reading." One of those words is problematic; the other is an outright lie.

The models are MATSUZAKI Shinjiro (you might remember him from Cruel Story of Youth), MIHARA Yuko (who now writes books about Japanese cinema with her husband), and SA(W|H)ARA Miyako (who has vanished so completely that Google returns 0 results.)

Behold: 『緑風を横切つて　今日は楽しいサイクリング』, or "Cut through the first winds of summer rustling in the green grass: today [let's enjoy some] pleasant cycling."

That grass looks so dry that it makes a mockery of the 緑 (green) in the title. Nor does it seem like the kind of foliage you want to ride through wearing only a swimsuit. Perhaps that's why she's walking.

Yes, after a bikini-clad ride through an overgrown briarpatch, nothing hits the spot like lying down on a pile of rocks.

Bike lane to the danger zone! Could these thrill-seeking crumb-bums possibly ride any less safely? Well...

Oh, yeah... she sure can. The Man can't make her wear no helmet, [hairstyle joke redacted], and he sure as hell can't stop her inhaling carcinogens as she goes.

Robert Heinlein used to dream about girls like this.