Oh No, I've Really Fallen for My Yandere Big Sister

After the protagonist, Lin Che, confesses on the rooftop to his unrelated older sister and gets rejected, his sister, Lin Wei, treats him coldly for a year. Now she's home for the holidays, and not only does she come over and ask if they should sleep together like they did when they were little, she also waits until Lin Che is asleep to steal a kiss in the middle of the night. But when she sees me talking to another girl, she quietly grips the fruit knife hidden in her bag and smiles as she asks, "Little brother, you'll stay with me forever, right?" His yandere big sister's possessiveness is off the charts, but she's gentle only with me. Let's see if I can turn her from a yandere into a clingy girlfriend!