[Kamitsuki Manmaru] Goodbye Big Sis (Inka no Mezame)

A curvaceous older stepsister visits her younger stepbrother and his father, joining a cozy dinner before getting adorably tipsy from a light drink. As the evening progresses, the boy discovers just how infatuated his voluptuous big sis is with him, leading to a steamy, forbidden encounter that ends with her tearfully confessing her love at his school wedding.