Kippei Katakura is a seventeen-year-old playboy. After her mother disappears his five-year-old cousin Yuzuyu comes to live with Kippei's family, he is suddenly in charge of taking care of her. Kippei is so busy trying to become Kokoro's boyfriend that he neglects Yuzuyu. He sleeps too late and doesn't have time to make her lunch and forgets to pick her up from kindergarten when spending an afternoon with Kokoro. Yuzu believes she's a burden to Kippei and decides to walk home by herself, disappearing somewhere on the way.