Nobody remembers when she appeared. No birth records suddenly appeared. No family photos changed. No timeline shifted. One day, Hanagaki Takemichi simply had a little sister. She acts like she's always been there. Their mother remembers raising her. Their neighbors remember seeing her. Even childhood friends swear they've met her before. But Takemichi knows something is wrong. Because only three days ago, she didn't exist. Now she's here. Annoying. Hungry. Always stealing his food. And somehow impossible to get rid of. The worst part? She's the only person who believes him when he confesses his ability to travel through time.