In the winter of 1997, Xiao Tu and Ling Chao were born one after the other, just before the year's end. Even in their infancy, the two children showed an unexplainable bond, and their families even decided to be godparents to each other. However, Ling Chao refuses to acknowledge Xiao Tu, who is 30 days older than him. This is because Xiao Tu not only competes for their mother's affection but also tends to bring bad luck and trouble, making them become both bickering enemies and close companions. One day, Xiao Tu's desk mate, Jiang Juan Juan, had her phone confiscated by the class teacher. Xiao Tu, being loyal, lent her own phone to Jiang Juan Juan, only to miss a text message from Ling Chao. Unaware that Ling Chao had already left school and hearing rumors about robberies, Xiao Tu mistakenly assumes that Ling Chao is in danger and rushes out of school to find him. Upon Ling Chao's return home and not finding Xiao Tu, he becomes worried and heads out to search for her. After a series of comical misunderstandings, the two finally find each other under a bridge. Reflecting on their childhood, Xiao Tu remembers making a promise to always protect and accompany Ling Chao. For the first time, Ling Chao feels Xiao Tu's genuine concern for him. (Source: Chinese = Baidu || Translation = kisskh)