Natsuzuma

Yumiko Seto is a young stay-at-home mother, happily on a beach vacation with her husband and son—or at least she would be, if her husband hadn't abandoned the two of them for dinner and drinks with his clients. Lucky for her, Yumiko meets two young men who are happy to entertain a lonely mother... and more than happy to appreciate her voluptuous figure, barely contained by a white string bikini. But when Yumiko realizes the two men have snapped a quick picture of the three of them, she'll do anything to make sure her husband never sees it—and maybe a little something to relieve her sexual frustrations as well...

(Source: J18)

The series has been published in English as Summer Affair: A Wife Seduced by Two Playboys by J18.