The drama tells the story of Tsukioka Natsu who dated her classmate Mizuki Nangumo during college, but one day when she was looking for a job, Mizuki suddenly proposed to break up. Seven years later, Natsu learned from a college friend that Mizuki had passed away. Natsu, who had never met after the breakup and had no sense of the fact, went to the funeral and met a little girl named Umi there. She was surprised to learn that she was Mizuki's daughter. Then, Mizuki's mother told him that he was Umi's father. Mizuki gave birth to a child in a place Natsu didn't know about, and raised her without saying anything. Natsu thought about the seven years that Mizuki and Umi had spent together.