May Your Misery Exceed Mine

In the first year of her marriage, Keiko Natori enjoys being a full-time housewife and having a great relationship with her husband. Surrounded by a circle of cherished friends, among them her dear younger sister Shiho, Keiko's life seems blissful in every aspect.
However, her happiness is shattered when her beloved sister betrays her trust by seducing her husband. Thus begins a tumultuous battle for affection between the two sisters, sparked by the flames of an illicit affair—who will emerge victorious in this emotional tug-of-war?
"Sister… I only wish for your misery to exceed mine."