Yue Zhi-Shi and Song-Yu are not blood related brothers, Yue Zhi-Shi, who was fostered by the Song family since childhood, loves to cling to his older brother, Song Yu, who is three years older than him. However, Song Yu always deliberately maintains a distance. Song Yu, the brother who pretends to be indifferent, and Yue Zhi-Shi, the brother who is a clingy little puppy. But what others don't know is that he understands his own heart, he choose to exercise self-control and maintain a distance because… Yue Zhi-Shi is Song-Yu’s only allergen.