Ten years ago, when Rin married their father, adult brothers Tatsuya and Kazuya were cheerful and sociable. After Tatsuya failed an entrance exam, he became a shut-in, and Kazuya gradually grew withdrawn and twisted as well. One day, Kazuya stares at Rin with clouded eyes and demands sexual relief. Afraid of what might happen if she refuses, she gives in to comfort him—only for Tatsuya to catch them.