Imouto ga Brocon de Aru koto wo Ani dake wa Shitteiru.

My younger sister’s devotion to me is genuinely terrifying. Akari Namiki is undeniably captivating—intelligent, beautiful, and effortlessly stylish. By contrast, I am nothing more than an entirely unremarkable background character. Yet the core issue I face is that my perfect sister harbors an overwhelming obsession with me. During my third year of middle school, I stumbled upon a notebook hidden in her room titled "Onii-chan Notes," which contained a meticulously detailed log of my every action and habit. Despite the cold, distant attitude she always projected toward me in person, the pages revealed a girl completely infatuated with her older brother. Worse still, I soon discovered that my own bedroom had been secretly wired with hidden surveillance cameras and listening devices. The situation escalated during the summer of my second year of high school when I uncovered Akari’s ultimate plan: to lock me away and make myself so dependent on her that I could no longer survive without her presence. Confronted with this chilling revelation, I made a firm decision right then and there. I resolved to interact with Akari strictly as a normal brother should, drawing a clear line while working to stop her dangerous fixation before it spirals entirely out of control.