Ritou no Hohoemi

Okada, an ordinary office worker, goes on holiday to a remote island where he meets mother and daughter, Kanae and China. Kanae, who is a tomboy and runs a guesthouse, has sex with the men on the island every night, while China, who is curious, sneaks into their futon and begs for sex. Okada is confused, but begins to be swept away. But the island has a little secret... (Source: Fanza, translated)