I'm Koichi Onoe. Three years ago, I married a woman named Waka, and we've been enjoying a happy marriage. Six months ago, my sister and her husband moved nearby and started visiting our home frequently, deepening our family bonds. However, my sister has always had a wild personality, and previously, she had sex at my house with my brother-in-law, during which I discovered he was extremely well-endowed. That made sense, as our marital and family relationships had been smooth with no apparent issues. But one day, I caught my wife and my brother-in-law in each other's arms, and my entire life was thrown into turmoil.