Returning home for childbirth, the wife stays at her parents' house. Concerned about her situation, her sister-in-law Aoi suddenly visits. Aoi is slender with big tits, flaunting her attractive figure. Claiming she'll stay overnight out of consideration, she even invades the bathroom. Caught between wanting to cherish time with his pregnant wife and the rekindled connection from their long-overdue conversation, he begins an illicit affair. However, unsatisfied with just one round, Aoi abandons all morals and dignity, surrendering to her instincts and escalating into an intense creampie session, flooding the wife's womb with a massive load of sperm.