I live in an apartment with my childhood friend Urara, whose breasts have grown increasingly large as she's gotten older. She's never been good at studying and often asks me to tutor her, though I never saw her as anything more than a friend. One day, I caught her having sex with my father, and after that shocking incident, I began to notice her large breasts. From that moment on, I couldn't stop thinking about them, gradually becoming drawn to her overwhelming charm.