Natsuzuma OVA

A married woman with her young son takes a summer vacation to the beach after her husband is called away on a business trip. While swimming, she meets two young men who befriend her and her son. Later that evening at their shared inn, the men manipulate her into posing in her swimsuit by taking compromising photographs, then coerce her into sexual acts by threatening to release the images. Despite her initial resistance and guilt over betraying her family, she becomes increasingly complicit in their advances, eventually surrendering to their manipulation and her own suppressed desires throughout the night.