"Brother, are you doing that again...?" I'm an awkward guy with poor eyesight, and my sweet younger sister Chiharu always worries about me. Though she sometimes finds me annoying, she still watches over me with warmth. In the midst of our daily lives, I suddenly hear the words: "You can't get a job because you're still a virgin." After that, Chiharu starts washing my entire body, giving me rimjobs, and carefully teaching me how to have sex. But will I truly be able to become a functioning adult? A heart-wrenching love story begins to unfold.