Having not returned home since moving to Tokyo, I finally went back to my parents' house after two years upon reaching my father's third death anniversary. There, I encountered a stunning, unfamiliar woman with massive breasts—my older brother's wife, who introduced herself as Kira-san. During my stay, I repeatedly witnessed the intense passion between my brother and my sister-in-law, which gradually overwhelmed my self-control. On the morning I was set to return to Tokyo, I decided to confess my feelings to Kira. But her response was something I never could have expected.