Marriage.On a snowy winter night, Nasa Yuzaki is lying on the street bleeding. During the time he believes he is going to die, he recalls his life, remembering how he was ridiculed for his unusual name and how he devoted his life to studying, wanting to attend an elite school. But before he was set to take the entrance exam, he was hit by a truck when he crossed the street trying to speak to a girl named Tsukasa Tsukuyomi. However, Nasa survives due to her intervention. After regaining consciousness, Nasa chases after Tsukasa wanting to go out with her as gratitude for saving his life, and Tsukasa agrees only if they get married when they are old enough to do so. After getting discharged from the hospital, he took the entrance exam the following year, but decided to work instead of attending high school, hoping to meet Tsukasa again. Shortly after turning 18, Tsukasa shows up at his apartment to fill out the marriage registration and submit it to the bureau to make the marriage official.