Umi to Ojousama to Kurokami Seiso na Bishoujo ni "Oneechan to Haramasete" to Onegai Sarete

"Will you help impregnate my sister?"

A beautiful and outgoing girl at his part-time job unexpectedly asks for his help to make a baby! His first love, now a chaste and glamorous married woman, sinfully coming inside her! The older sister, Yuuki, becomes pregnant with the fruit of their love, and the younger sister, Aika, gives up her virginity. Their feelings deepen, and the love affair with two sisters by the sea is like a dream.......

(Source: France Shoin, translated)